3-Amino-2-hydroxy, halo or mercaptomethyl-4-oxoazetidines

ABSTRACT

The stereospecific cycloaddition of nitrogen containing acetic acid halides or anhydrides with Schiff bases having a carbalkoxy group substituted on the methine carbon atom offers new intermediates and methods for preparing synthetic cephalosporin congeners having antibacterial activity.

This is a division of application Ser. No. 821,386, filed Aug. 3, 1977,now U.S. Pat. No. 4,166,816, which is a continuation-in-part ofapplication Ser. No. 696,094, filed June 14, 1976, now U.S. Pat. No.4,072,674, which in turn is a continuation-in-part of our applicationSer. No. 626,686, filed Oct. 29, 1975, now abandoned, which is acontinuation-in-part of our application Ser. No. 574,225, filed May 5,1975, now abandoned.

This invention relates to cephalosporin-like compounds which haveantibacterial activity and to chemical compounds and methods useful toprepare these novel antibacterial agents.

BACKGROUND

Cephalosporins obtained by fermentation processes or ring expansion ofpenicillins all contain the 8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-enenucleus, i.e. ##STR1## Compounds with this ring system have been theobject of intense research and numerous scientific articles and patents.As a result of this effect, approximately eight commercial products areavailable today as antibacterial agents.

Analogous rings systems in which the sulfur atom has been moved toanother position in the six-membered ring can not be obtained by thesame methods as described for the above nucleus. A totally syntheticapproach to this ring system must be employed. One system which has beenattempted with varied success is the8-oxo-4-thia-1-azabicyclo[4.2.0]octane for which the trival nameisocephalosporin can be given, i.e. ##STR2##

The synthesis of7β-phenylacetamido-7α-methyl-6αH-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacid and the 2,3-dihydro derivative has been reported in J. Chem. Soc.1321 (1973). These compounds lack the 2-3 double bond believed necessaryfor biological activity and/or have a 7α-methyl group which is notpresent in naturally occurring cephalosporins. These two compounds werereported to have no antibacterial activity when tested at high levelsagainst three bacteria. Also reported within this reference was aderivative with trans-configuration,7α-phenylacetamido-6αH-8-oxo-4-thia-1-aza-[4.2.0]octane-2-carboxylicacid. This compound also showed no activity. Within this referenceattempts to prepare the nucleus without the methyl substituent and withthe 2-3 double bond were unsuccessful. Further attempts were reported inJ. Chem. Soc. Perkin I, 2092 (1974) and were also unsuccessful.

We have now prepared the 6,7αH-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-enering system; in particular,7β-acylamino-6αH-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacids and derivatives thereof.

SUMMARY OF THE INVENTION

The compounds of this invention are represented by the followingstructural formula: ##STR3## wherein R is an acyl group and

E is hydrogen, methyl, bromomethyl, or lower alkanoyloxymethyl.

The term acyl group refers to any acyl group used within thecephalosporin and penicillin art, except phenylacetyl. Preferred acylgroups are represented by the general formulae: ##STR4## Especiallypreferred acyl groups are those where X is thienyl, cyclohexyl,cyclohexenyl, cyclohexadienyl, phenyl, or phenyl substituted with one ortwo substituents selected from the group consisting of lower alkyl,lower alkoxyl, hydroxy, hydroxymethyl, halo, nitro, amino, aminomethyl,mercapto, lower alkylthio, trifluoromethyl, ureido, formamido, andcarboxymethylamino; A' is amino, hydroxy, formyloxy, carboxyl, orsulfonic acid; Y is cyano, azido, phenoxy or a 5 or 6-memberedheterocyclic ring containing 1-4 heteroatoms selected from the groupconsisting of nitrogen, oxygen and sulfur; Z is phenyl, pyridyl, loweralkyl, trifluoromethyl, trifluoroethyl, or cyanomethyl and n is 0, 1 or2. The 5 or 6-membered heterocycles include thienyl, furyl, thiazolyl,isothiazolyl, oxadiazolyl, thiadiazolyl, triazolyl, tetrazolyl, sydnone,pyridyl, pyrimidyl and the like. The heterocyclic group may beunsubstituted or substituted with substituents selected from loweralkyl, halo, hydroxy, nitro, amino, lower alkoxy, aryl such as phenyl,lower aralkyl and the like.

The terms lower alkyl, lower alkoxy and lower aralkyl used within thisentire disclosure refers to alkyl groups containing one to six carbonatoms. The term halogen or halo includes fluorine, chlorine and bromine.

The compounds which are also a part of this invention and which areuseful as intermediates to prepare compounds of Formula I arerepresented by Formula II: ##STR5## wherein E is hydrogen, methyl,bromomethyl or lower alkanoyloxymethyl;

W is R'₂ N;

R² is hydrogen or removable carboxyl protecting group; and

each R' is hydrogen or a monovalent removable amine protecting group orwhen both R' groups are taken together, a divalent amine protectinggroup.

Lower alkanoyloxymethyl in both Formulae I and II refers to alkanoylgroups of one to six carbon atoms. A preferred member within this groupis acetoxymethyl.

Another group of compounds which are a part of this invention and areuseful intermediates for the preparation of the compounds of Formulae Iand II are represented by Formula III: ##STR6## wherein A is N₃, NH₂,acylamino, or protected amino;

B is COOY or CH₂ X';

Y is hydrogen or lower alkyl;

X' is OM, halogen, p-methoxybenzylthio, triphenylthio, or mercapto;

M is hydrogen, lower alkylsulfonyl or phenylsulfonyl, said phenyl beingunsubstituted or substituted with methyl or halogen; and

Z is hydrogen or 2,4-dimethoxybenzyl.

The term "removable carboxyl protecting group" is a term which hasacquired a definite meaning within the cephalosporin and organicchemical arts. Many groups, particularly many ester groups, are knownwhich are used to protect the carboxyl groups during subsequent chemicalreactions and later removed by standard methods to give the freecarboxylic acid group. Known ester protecting groups include2,2,2-trichloroethyl, C₄ -C₆ -tert-alkyl, such as t-butyl, C₅ -C₇-tert-alkenyl, C₅ -C₇ -tert-alkynyl, C₁ -C₆ -alkanoylmethyl,N-phthalimidomethyl, benzoylmethyl, halobenzoylmethyl,methylbenzoylmethyl, methanesulfonylbenzoylmethyl, phenylbenzoylmethyl,benzyl, nitrobenzyl, methoxybenzyl, benzhydryl, trityl, trimethylsilyl,triethylsilyl and the like. The choice of which ester group to use iswell within the ability of one skilled in the art. Factors which areconsidered include what subsequent reaction conditions the group mustwithstand and what conditions for removing the protecting ester isdesirable. Groups which are removed by treatment with trifluoroaceticacid, hydrogenation or zinc dust and acetic acid have been preferred inthe art when a β-lactam is fused to a six-member ring. The choice of theprotecting group is not critical to our invention since the novelty ofour invention lies within the new bicyclic nuclei and not the estersubstituents.

A "removable amine protecting group" or a "protected amino group" areterms well known in the art. They refer to amino groups which have beenmasked by another group so as to protect them during subsequent chemicalreactions and then the masking group can be removed to generate againthe desired amino moiety. Many groups are known and used for thispurpose within the penicillin, cephalosporin, and peptide syntheticarts. Examples of these include, t-butoxycarbonyl,trichloroethoxycarbonyl, benzyloxycarbonyl, p-methoxybenzylcarbonyl,isobornyloxycarbonyl, trityl, methyl acetoacetate adduct and the likewhich are monovalent protecting groups. Divalent protecting groupsinclude phthaloyl and the 4,5-diphenyl-4-oxazolin-2-one group. Treatmentof a phthalimido group with hydrazine by published procedures cleavesthe phthaloyl group to regenerate the amino group. Preparation andremoval of the 4-oxazolin-2-one group is taught in the art; J. Org.Chem., 38, 3034 (1973). The choice of the protecting group depends onvarious factors including the subsequent chemical reaction conditionsand the desired conditions for removal of the protecting group. However,this choice is within the ordinary ability of one skilled in the art.Again the choice of the amino protecting group is not critical to ourinvention for the same reasons given above about the carboxyl protectinggroup.

The term acyl group means any acyl group which has been used in thesemisynthetic penicillin and cephalosporin fields except phenylacetylincluding the following examples:

α-hydroxyphenylacetyl

α-formyloxyphenylacetyl

α-aminophenylacetyl

α-amino-4-hydroxyphenylacetyl

α-amino-4-hydroxy-3-fluorophenylacetyl

α-amino-4-carboxymethylaminophenylacetyl

trifluoromethylmercaptoacetyl

methylmercaptoacetyl

methylsulfonylacetyl

2,2,2-trifluoroethylsulfinylacetyl

cyanoacetyl

cyanomethylmercaptoacetyl

cyanomethylsulfinylacetyl

cyanomethylsulfonylacetyl

α-carboxy-2-thienylacetyl

α-carboxy-3-thienylacetyl

α-carboxyphenylacetyl

α-sulphophenylacetyl

3-sydnoneacetyl

2-thienylacetyl

3-thienylacetyl

1-tetrazolylacetyl.

The compounds of this invention set forth in Formulae I and II contain anucleus which is related to naturally occurring cephalosporins but whichcannot be prepared by fermentation methods. Therefore, the compounds areprepared by a totally synthetic route as outlined in Scheme I. WithinScheme I, R is any acyl group as set out above or a derivative thereofin which any chemically sensitive group such as carboxy, hydroxy oramino is protected with a standard removable protecting group, many ofwhich have been described above, until the final step of the reactionsequence. Many protective groups are set forth in the book "ProtectiveGroups in Organic Chemistry", ed. J. F. W. McOmie, Plenum Press, NewYork, 1973 and in other review articles and books. R' is an aminoprotecting group which is removed after the4-thia-1-azabicyclo[4.2.0]-oct-2-ene nucleus is formed to give the7-amino derivative. This derivative can then be acylated by the samestandard methods used within the cephalosporin art with the desired acylgroup to give the compounds of this invention. R² is a protective esterresidue used to protect the carboxyl group and is also removable at theend of the reaction sequence to give the final active products whichcontain a free carboxyl group or a salt thereof. ##STR7##

The important intermediate which gives the new nucleus its 6,7-cisconfiguration is methylcis-1-(2,4-dimethoxybenzyl)-3-azido-4-oxoazetidine-2-carboxylate (3).This compound is prepared by the cycloaddition reaction between theimine obtained from the condensation of 2,4-dimethoxybenzylamine andmethyl glyoxalate and a mixed anhydride or acid halide of azidoaceticacid. The azido group of this intermediate is reduced by catalytichydrogenation or by chemical reduction such as zinc and acetic acid togive the 3-aminoazetidine derivative. The amino group can be protectedby a removable amino protecting group such as t-butoxycarbonyl. Aprotected 3-aminoazetidine derivative can also be prepared directly bysubstitution of a glycine derivative in which the amino group has beenprotected. For example, 4,5-diphenyl-2-oxo-4-oxazolin-3-ylacetic acid orN-phthalimidoacetic acid can be used in the cyclization reaction in thesame manner as azidoacetic acid to give the corresponding protected3-aminoazetidine derivative.

The intermediate 3 or a protected 3-aminoazetidine described above canbe converted by a series of reactions into the 2-methylsulfonatederivative as illustrated by compound 11 in Scheme II. Varied reactionsequences can be used in the preparation of compounds like 11 Scheme IIsets forth two alternate pathways which can be used to go from compound3 to compound 11. It is apparent to persons skilled in the art thatconversion of the azido group to the protected amino is not limited tothe two illustrated places along the reaction sequence but can also bedone at other alternative places. Reduction of the azido moiety isadvantageously done on compound 3 in Scheme II or on the3-azido-2-methyl tosylate derivative 12.

The methylsulfonate derivative (11) is then converted stepwise to themercaptomethyl derivative 7 as set forth in Scheme III. The sulfonate isdisplaced with iodide in which is in turn displaced with a mercaptanderivative such as p-methoxybenzyl mercaptan or triphenylmethylmercaptan. Cleavage of these derivatives by standard synthetic methodsgives the mercaptomethyl compound 7. The p-methoxybenzyl group iscleaved by treatment with mercuric salts. The triphenylmethyl group iscleaved by treatment with silver salts including silver nitrate andsilver tetrafluoroborate and therefore is advantageous if other groupswithin the compound are sensitive to mercuric ion. ##STR8##

The mercaptomethyl compound 7 is reacted with a β-bromo-α-keto ester togive the bicyclic system as shown in compound 8. When a bromopyruvateester is used, compound 8 where E is hydrogen is obtained. When a3-bromo-2-ketobutyrate ester is used, compound 8 where E is methyl isobtained. These compounds are dehydrated to give the8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene system 9. Standard dehydrationreagents such as thionyl chloride, trifluoroacetic anhydride, andmethanesulfonyl anhydride are used.

Compounds of structure 9 where E is bromomethyl are prepared by radicalbromination of the 3-methyl compounds using the procedures known in thecephalosporin art. Bromination reagents include N-bromosuccinimide inthe presence of radical initiators such as benzoyl peroxide orazobisisobutyronitrile.

The bromomethyl derivatives can be reacted with various acetic salts togive compounds of structure 9 where E is acetoxymethyl. Exemplary saltsuseful for this purpose include sodium, potassium, or silver acetate.

Compounds of structure 10, the antibacterial agents of this invention,are prepared from compounds of structure 9 by removal of the aminoprotecting group followed by acylation with the desired acyl group usingstandard acylation methods. Following the acylation any additionalprotecting groups are removed. During the acylation reaction anysensitive groups such as amino or hydroxy are protected as has beenpreviously described. Standard acylation methods include activation ofthe carboxyl by use of mixed anhydrides, activated esters, and acidhalides or by use of coupling reagents such as dicyclohexylcarbodiimide.

Some compounds within the scope of Formula I can alternatively beprepared by acylation with the desired acyl group earlier in thereaction sequence. For example, the 3-aminoazetidone derivative can beprepared and acylated at the same places as those disclosed in SchemeII. When this acylated monocyclic β-lactam is carried along the reactionsequence herein disclosed the desired final products are obtained.Examples of acyl groups for which this alternate method can be usedinclude phenoxyacetyl, α-aminophenylacetyl,α-amino-p-hydroxyphenylacetyl, 2-thienylacetyl and the like.

More specifically, when 2,4-dimethoxybenzylamine [Chem. Ber., 101, 3623(1968)] is condensed with methyl glyoxalate [Synthesis, 544 (1972)],imine 1 is obtained. Reaction of this imine with the mixed anhydride oftrifluoroacetic acid and azidoacetic acid [Tetrahedron Lett., 2319(1973)] gives methylcis-1-(2,4-dimethoxybenzyl)-3-azido-4-oxo-2-azetidinecarboxylate (3).This reaction can be run as a two-step process by first generating themixed anhydride and then adding this to a solution of the imine.Alternatively, a one step procedure can be used in which the azidoaceticacid is added to a solution of the imine followed by the addition of thetrifluoroacetic anhydride. In addition, other glyoxalate esters such asethyl or propyl can be used in the same manner.

The 2,4-dimethoxybenzyl group is removed by oxidative methods. Forexample, treatment of the N-(2,4-dimethoxybenzyl)β-lactam with potassiumpersulfate effects the deblocking reaction to generate the freeβ-lactam. This reaction is carried out in the presence of sodiummonohydrogen phosphate. With some derivatives, pH control during thereaction within a range of 5-6 may be advantageous to the reactionyield. Under these conditions we have found that the benzyl group is notremoved like the dimethoxybenzyl group. However, one skilled in the artcould try other substituted benzyl moieties and determine if they areremovable and therefore are also able to perform the same function asthe dimethoxybenzyl group.

Reduction of the 2-alkoxycarbonyl group with suitable reducing agentssuch as sodium borohydride gives the 2-methyl alcohol derivative. Inparticular, the methoxycarbonyl group is readily reduced with sodiumborohydride to give the alcohol derivative.

The alcohol derivative can also be prepared by reduction of the2-carboxylic acid by standard reduction methods known in the art. Theacid is prepared from the ester derivative by base hydrolysis. Forexample, the methyl ester hydrolyzes to the carboxylic acid by treatmentwith sodium carbonate, potassium carbonate or similar base. Thecarboxylic acid can be converted to its acid chloride and reduced withsodium borohydride to give the desired alcohol moiety. The1-(2,4-dimethoxybenzyl)-2-carboxylic acid derivatives can be reduced tothe 2-methyl alcohol derivative which can be converted to thecorresponding tosylate. The dimethoxybenzyl group can be removed at thispoint to give the β-lactam methyl tosylate precursor which can becarried further as has been described.

The alcohol is treated with p-toluenesulfonyl chloride, benzenesulfonylchloride, p-bromobenzenesulfonyl chloride, mesyl chloride or similarreagents which convert the alcohol into a group which is readilydisplaced by iodide ion by nucleophilic displacement. Standardnucleophilic displacement of the sulfonate moiety with iodide followedby another nucleophilic displacement with sulfur derivatives gives themercapto methyl moiety or a group which can be converted to the desiredmercapto methyl compound. Triphenylmethylmercapto andp-methoxybenzylmercapto are typical groups which readily cleaved to thefree mercapto group as set out above.

The new cephalosporin-like nucleus is generated by a cyclizationreaction of the mercaptomethyl compound and a bromopyruvate derivative.The product formed contains a hydroxy group alpha to the carboxyl group.Dehydration of this hydroxy group places the double bond in the nucleusat the 2,3-position analogous to the cephalosporin series. Dehydrationis best carried out with thionyl chloride or trifluoroacetic anhydrideand pyridine.

The starting materials for the compounds of this invention arecommercially available, prepared by known methods or described herein.

Also included within the scope of this invention is the pharmaceuticallyacceptable non-toxic salts of the active compounds or esters easilydegraded to the active compound in vivo. These include the salts of thecarboxylic acid at position 2 or within the acyl sidechain and the acidaddition salts of any basic substituent present in the compound.Carboxylic acid salts include those where the cation is an alkali metalsuch as sodium or potassium, alkaline earth such as calcium, or anammonium cation such as ammonium, cyclohexylamine and the like. The acidaddition salts are prepared from those acids known and used inpharmaceutical preparations including both inorganic and organic acids.The salts are prepared by the standard methods well-known in the art.

The compounds of this invention within Formulae I and II exist in thecis configuration at positions 6 and 7. The compounds also exist asoptical isomers. Included within the scope of this invention is theseparate optical isomers as well as any mixtures thereof.

The compounds of Formula I of this invention have antibacterial activityagainst both Gram-positive and Gram-negative bacteria. For example,7-phenoxyacetamido-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacid has antibacterial activity against Staphylococcus aureus andShigella paradysenteriae. The compound7-(α-aminophenylacetamido)-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacid has additional activity against Escherichia coli, Klebsiellapneumoniae, Serratia marcescens, Salmonella paratyphi, Shigellaparadysenteriae, and Enterobacter species. The 2-thienyl congener isalso very active. The compounds are useful for the treatment andprevention of bacterial infections as well as for sterilization ofequipment, glassware and the like. Further details are available in ourcopending application Ser. No. 693,992, filed June 8, 1976 now U.S. Pat.No. 4,103,086.

The compounds of Formulae II and III are useful as chemicalintermediates in the preparation of novel cephalosporin-like compoundsof Formula I as has been described herein. Compounds within Formula IIwhere W is amino (NH₂) can be acylated as described above with any ofthe acyl groups known in the cephalosporin or penicillin arts to givecompounds which, after removal of any ester protecting group, haveantibacterial activity. Compounds within Formula II where R' is an aminoproprotecting group are useful to prepare the compounds where R' ishydrogen.

The compounds claimed here are the valuable intermediates of Formula IIIabove with the groups at Y and Z expanded to include equivalent groupsas will be disclosed herein. The compounds of key subgeneric groups arethe compounds (a) in which B is carbalkoxy (that is, for example, B is##STR9## lower alkyl); (b) in which B is carbalkoxy and Z is2,4-dimethoxybenzyl; (c) in which B is carbalkoxy and Z is hydrogen; or(d) in which B is tosyloxymethyl and Z is hydrogen.

Individual compounds of this part of the invention which areparticularly useful are those of Formula III in which:

A is azido, B is carbethoxy and Z is 2,4-dimethoxybenzyl;

A is azido, B is carbethoxy and Z is hydrogen;

A is azido, B is carbomethoxy and Z is 2,4-dimethoxybenzyl;

A is azido, B is carbomethoxy and Z is hydrogen;

A is amino, B is carbomethoxy and Z is 2,4-dimethoxybenzyl;

A is amino, B is carbomethoxy and Z is hydrogen;

A is phthalimido, B is carbomethoxy and Z is 2,4-dimethoxybenzyl;

A is phthalimido, B is carbomethoxy and Z is hydrogen;

A is azido, B is tosyloxymethyl and Z is hydrogen;

A is phenoxyacetamido, B is carbomethoxy and Z is hydrogen;

A is tert.-butoxycarbonylamino, B is carbomethoxy and Z is hydrogen;

A is azido, B is hydroxymethyl and Z is hydrogen;

A is tert.-butoxycarbonylamino, B is mercaptomethyl and Z is hydrogen;

A is 4,5-diphenyl-2-oxo-4-oxazolin-3-yl, B is carbomethoxy and Z ishydrogen.

The intermediates of Formula III are distinguished by being exclusivelycis-4-oxo-azetidines as noted above. Also included where appropriate arethe salt derivatives often used standardly in synthetic procedures. Thatis acid addition salts where basic amine function is present, such ashydrohalide, tosylate, acetate, mesylate, sulfate, nitrate, etc., oralkali metal salts such as the sodium or potassium salt if an acidicfunction such as carboxylic acid is present. As far as we are aware, thecis-4-oxo-azetidines claimed herein are novel. Belgian Pat. No. 772,940discloses a process for preparing a large number of azetidinones usingan ozonolysis reaction but the preparation of the starting materials forthe process is unclear. The configuration of the end product ispredominantly in the unfavorable trans position. No carbalkoxy esters atthe 2-position are specifically mentioned in this reference. Also U.S.Pat. No. 3,943,123 discloses certain carboxy aryl or aralkylazetidinesbut no stereospecific formation of the desired cis-series.

Also a part of the invention claimed here are two key chemicalreactions. The first of these is a cyclization to give a cis-azetidinoneby reacting a carbalkoxyl containing imine (1a) with a reactive acylhalide or mixed anhydride formed from an azidoacetic acid (2a). In placeof the azido radical one can alternatively use a "protected", or"blocked" amino or an "acylamino" as described herein: ##STR10## inwhich alk is lower alkyl of 1-6 carbon atoms but substituted orunsubstituted, straight or branched as defined hereafter such as methyl,ethyl, trichloroethyl or benzyl; DMB is 2,4-dimethoxybenzyl or itsequivalent; A is azido, "protected" amino or "acylamino"; and P is thehalo residue of the acid halide, preferably chloro or bromo, or thereactive portion of the mixed anhydride such astrifluoromethylcarbonyloxy, benzoyloxy, lower alkanoyloxy, loweralkoxycarbonyloxy, benzyloxycarbonyloxy or halo lower alkoxycarbonyloxy.The azido acetic acid chloride or trifluoroacetic acid mixed anhydridereagents are preferred reactants for 2a. The acid chloride reagents areof particular use for the protected amino or acylamino containing 2areagents.

The term "protected" amino defines any group which masks or blocks theundesired chemical vulnerability of the amino function during reactionbut which is readily removed when desired. Many such are known to thepolypeptide or antibiotic arts. Exemplary are tert.-butoxycarbonylamino(t.boc), trichloroethoxycarbonylamino, benzyloxycarbonylamino,p-methoxybenzylcarbonylamino, isobornyloxycarbonylamino, tritylamino,benzhydrylamino, methylacetoacetate imino adduct, phthalimido,succinimido, maleimido, 4,5-diphenyl-2-oxo-4-oxazolin-3-yl,2,6-dimethoxybenzoylamino or p-nitrobenzoylamino.

Suitably protected "acylamino" acetyl chlorides or anhydrides which canbe used for this invention include those listed herebefore. Exemplary ofthese are the starting materials in which compound 2a isphenoxyacetylaminoacetyl chloride, O-benzylmandeloylaminoacetyl chloride(which gives cis-3-mandeloylamino-2-carbomethoxy-4-oxoazetidine aftercyclization followed by catalytic hydrogenation of the protectiveO-benzyl group), D-α-tert.-butoxycarboxamidophenylacetamido acetic acid(reacted as the mixed anhydride with isobutylchloroformate, then thet.-boc group split using trifluoroacetic acid as in U.S. Pat. No.3,867,380), O-formylmandeloylaminoacetylchloride, cyanoacetamidoacetylchloride or N-methyl-1-tetrazolylacetamidoacetyl chloride.

It should be understood that the term "acylamino" is used solely fordescribing such pharmaceutically acceptable groups known to thecephalosporin art at the 7-position or their known synthetic precursors.These are distinct from "protective" groups whose sole function is toprotect the amine function during cyclization or oxidative degradation.

In the term "protected amino" advantageous compounds in regard to yieldof the cycloaddition reaction are those with amino substituents in whichboth amino hydrogens are replaced in effect with bifunctional orbivalent protecting groups. Exemplary of these bifunctionally protectedamino groups are phthalimido, succinimido, maleimido or4,5-diphenyl-2-oxo-4-oxazolin-3-yl. The monovalent or monofunctionalprotective groups as well as the "acylamino" groups as defined aboveundergo cycloaddition with heavy formation of by-products and in verylow yields of β-lactam containing material. These compounds are bestprepared by standard reaction with the 3-aminoazetidinone derivative inthe reaction sequence. That is with the 3-aminoacetidinone after thecycloaddition reaction.

The "alk" portion of the structures presented herebefore as in 1a, 3a orFormula III as a portion of the carbalkoxy substituent in the Schiff andon the subsequently formed 4-oxoazetidines represents part of any easilyremoved ester moiety. For convenience it is a branched or unbranchedaliphatic chain of from 1-6 carbon atoms which may be optionallysubstituted by conventional substituents in the art such as halos orphenyl. Since the group is eliminated in the later steps of thesynthetic sequence wide variability is possible but not necessary forthe reaction overall. Most useful are the carbomethoxy and carbethoxymoieties but "alk" may be any aliphatic moiety derived from the alkglyoxate starting material for example trichloroethyl, n-butyl, isoamyl,benzyl, methoxybenzyl, phenethyl, t-butyl, benzhydryl, isopropyl, etc.

The cycloaddition of imines or Schiff bases and azidoacetic acid in theform of its acid chlorides or anhydrides is known to the art [forexample the work of A. K. Bose et al., Tetrahedron, 23, 4769 (1967) upto Tetrahedron Letters, 22, 1917 (1974) especially Tetrahedron Letters26, 2319 (1973) and U.S. Pat. No. 3,943,123]. Most of the reportedcycloadditions have one or more aromatic substituents in the iminereactant. The addition most often favors forming the undesirable transazetidine or a mixture of cis-trans isomers. In certain cyclic or highlysubstituted series cis addition has been reported, J. Org. Chem. 29,3632 (1964).

As far as we know the use of phenyl or benzyl imines or Schiff bases (orazomethines) which have a carbalkoxy group substituted on the methinecarbon atom is novel to give exclusively cis-azetidinones. Also theability to remove the N-benzyl substituent from the azetidinones in oneoxidative step is novel.

The cycloaddition reaction comprises reacting the imine (1a) with thereactive acid halide or mixed anhydride (2b) in an aprotic solvent wichis inert under the reaction conditions and in which the reactants arereasonably soluble. For example, the solvent may be a chloro-containinghydrocarbon such as methylene chloride, carbon tetrachloride orchloroform; an aromatic solvent as benzene or toluene; tetrahydrofuran;dioxane; dimethylsulfoxide; hexamethylphosphoramide; ethyl acetate;acetonitrile; ether; dimethylformamide or dimethylacetamide; or mixturesthereof. The solvent is not critical but methylene chloride is oftenused. The reaction temperature may be from just above the freezing pointof the mixture up to room temperature. Certain reactions may be run atabout -30° to -80° C. Most useful are temperatures of from about -30° to5° C. The reaction may take from about one-quarter to eight hours. Mostoften the reaction is run in an ice bath for several hours.

As noted the cyclization reaction to produce the monovalently protectedor acyl containing azetidine amino compounds generally speaking giveslower yields than it does using the azido-containing or bivalentlyprotected amino acetic acid derivative. The latter reaction is,therefore, a most useful one.

The second key reaction is the removal of the N-dimethoxybenzyl groupfrom the azetidone compounds of Formulae 3, 3a or 4: ##STR11##

The term DMB is used to define the very useful 2,4-dimethoxybenzylN-substituent. For the good yield aralkyl N-substituents having apotentially very stable free radical form is necessary. This isaccomplished by more than one phenyl substituent such as using thebenzhydryl substituent or using electron releasing substituents on thearomatic ring such as methoxy or ethoxy groups or both such as withmethoxy substituted benzhydryl. With protective aralkyl groups havingpotential of forming very stable benzylic type radical forms othersplitting reaction conditions can be alternatively used such as withtrifluoroacetic acid.

For practical purposes the 2,4-dimethoxy benzyl protective group is mostuseful. The methoxy groups on the benzhydryl may be at one or more ofthe two o or p positions of both phenyl rings.

The removal of the N-protective moiety is necessary for conversion ofthe azetidone compounds to end products having antibacterial activity.The removal of the ring nitrogen substituent is accomplished by thereaction with those oxidizing agents which furnish a hydroxy radical.Organic chemists skilled in synthetic procedures will recognize thisclass of oxidizing agents. For example, the inorganic persulfates,especially potassium or sodium persulfate, are useful. Alternativesplitting reagents may be used for example the organic peracids, such asperbenzoic or peracetic acid or N-bromosuccinimide or in some instancestrifluoroacetic acid.

The solvent for the splitting reaction is any inert solvent in which thereactants are soluble. In the case of the persulfates, acetonitrile,acetone, dioxane or aqueous mixtures thereof are used. The reactiontemperature may vary from room temperature to the reflux temperature ofthe mixture. A useful range is from about 60°-100° C. Convenientlyaqueous acetonitrile at reflux temperature until the reaction iscomplete may be employed. This is usually from one to eight hours,depending on the scale. The azetidinone starting materials may bemonitored during the reaction.

The oxidizing reaction may be applied to any azetidinone bearing asusceptible methoxybenzyl-like blocking group at position 1 as discussedabove for example, those of Formula I in which the 1-nitrogen is blockedby a dimethoxybenzyl, benzhydryl or methoxybenzhydryl group. Also thepresence of easily oxidized functions such as thiophene in the molecule,for example at the 3-acylamino reaction, may affect the specific courseof the oxidation. If such problems arise the 3-acyl moieties must beattached to the ring after debenzylation. Any other susceptible groupssuch as hydroxyl or amino should be masked as known to the art.

Most conveniently the pH of the oxidation reaction is controlled by anyconvenient buffer system, for example using sodium acid phosphatesystems, boric acid-borax, secondary sodium citrate. The mixture shouldbe close to neutral, say about 5-8 especially about 6.

The reaction proceeds most smoothly with potassium persulfate in aqueousacetonitrile at reflux in a substantially neutral reaction mixture. TheN-2,4-dimethoxybenzyl substituent at the 1 or N-position of the2-carbomethoxy-3-azido-4-oxoazetidine system is removed under theseconditions in about 60-70% yield.

One skilled in the art will recognize that the compounds of claim 1 andof Formula III have groups and/or radicals which may not be chemicallystable under all conditions and in all environments. Any suchconflicting groups may be suitably masked for that compound to serve asan intermediate for further synthesis. PG,29

The reaction mixtures of both key reactions are worked up by standardmethods as will be evident from the working examples. In thedebenzylation aldehyde such as dimethoxybenzaldehyde is generated by theoxidation.

The following are specific embodiments of this invention to teach theinvention to those skilled in this art.

PREPARATION 1 Methyl N-(2,4-dimethoxybenzyl)iminoacetate

To a mixture containing 16.82 g (0.101 mole) of 2,4-dimethoxybenzylamineand anhydrous magnesium sulfate in 150 ml of methylene chloride at 25°is added a solution of 10.05 g (0.114 mole) of methyl glyoxalate in 20ml of methylene chloride. The reaction mixture is stirred at roomtemperature overnight (15 hours) and then is filtered and the solventsare removed in vacuo to afford the imine as a dark orange gum.

PREPARATION 2 4,5-Diphenyl-2-oxo-4-oxazolin-3-ylacetic acid chloride

A mixture of 4,5-diphenyl-2-oxo-4-oxazolin-3-ylacetic acid (2.1 g, 7.1mmol) [J. Org. Chem., 38, 3034 (1973)], thionyl chloride (5 ml) andmethylene chloride (20 ml) is refluxed for 2.5 hours. After cooling toroom temperature the solvent is removed in vacuo and resulting oilcrystallizes on standing. The product is triturated with ether-hexane togive the title compound; 2.0 g mp 104°-112°.

PREPARATION 3 Bromopyruvate Esters

To a solution of 3.3 g (37.5 mmole) of pyruvic acid and 7.9 g (37.5mmole) of trichloroethyl chloroformate in 20 ml of dry tetrahydrofuranat 0° is added dropwise 0.6 ml of pyridine. After stirring for 2 hoursat room temperature, the mixture is concentrated in vacuum, diluted withwater and extracted with ethyl acetate. The extract is washed with 5%HCl, dried over MgSO₄, evaporated and distilled in vacuum to give 4.0 g(50%) trichloroethyl pyruvate, bp 75°-82° (17 mm).

Trichloroethyl pyruvate (3.7 g, 1.7 mmole) is heated to 65° and 1.1 ml(17 mmole) of bromine is added dropwise over 1 hour. A stream of carbondioxide is passed through the reaction mixture during the addition toremove the HBr formed in the reaction. The mixture is cooled to roomtemperature, diluted with water and extracted with ethyl acetate. Theextract is dried over MgSO₄, evaporated and distilled in vacuum to give1.8 g of trichloroethyl bromopyruvate, bp 74°-77° (0.01 mm).

Bromopyruvic acid is treated with diphenyldiazomethane by standardmethods to give benzhydryl bromopyruvate.

The t-butyl ester is also prepared by standard methods of reactingO-t-butyl-N,N'-diisopropylpseudourea [Ann. Chem., 597, 235 (1955)] andbromopyruvic acid.

PREPARATION 4 3-Bromo-2-ketobutyrate esters

At room temperature under argon 1.85 g (9.6 mmol) ofdiphenyldiazomethane in 15 ml of dry benzene is added dropwise to asolution of 1.30 g (7.35 mmol) of 3-bromo-2-ketobutyric acid in 15 ml ofdry benzene with vigorous stirring. Addition of the diazo compound iscontinued until a faint red color persisted (0.5 hr). The solvent isremoved in vacuo and the yellow oil is dissolved in ether, filtered andconcentrated to give 3.12 g crude benzhydryl ester. Chromatography onsilica gel eluting with benzene affords 2.43 g (95%) pur benzhydryl3-bromo-2-ketobutyrate as a yellow oil.

A solution of 1.6 g (8.85 mmol) of 3-bromo-2-ketobutyric acid and 7 g (4equivalents) of O-t-butyl-N,N'-diisopropylpseudourea in 14 ml methylenechloride is stirred overnight at room temperature. After filtration, thesolution is washed with NaHCO₃ and brine, dried and evaporated to an oilwhich is chromatographed on silica gel with benzene as eluant to give 1g (45%) of t-butyl 3-bromo-2-ketobutyrate.

EXAMPLE 1 Methylcis-1-(2,4-Dimethoxybenzyl)-3-azido-4-oxoazetidine-2-carboxylate

Method A

To a solution of 15.1 g (0.149 mole) of azidoacetic acid in 130 ml ofanhydrous methylene chloride at 0° (ice bath) is added dropwise 21.0 ml(0.15 mole) of trifluoroacetic anhydride. This mixture is stirred at 0°for 15 minutes and then 20.8 ml (0.15 mole) of triethylamine is addeddropwise. Stirring is continued for an additional 45 minutes and thenthe entire reaction mixture is transferred under argon into anadditional funnel which is cooled externally by dry ice. The additionalfunnel is attached to a flask containing the imine from Preparation 1,anhydrous methylene chloride (200 ml), and triethylamine (20.8 ml, 0.15mole). The solution of the mixed anhydride is added dropwise from theaddition funnel to the solution of imine at 0°. Stirring is continued at0° for 1 hour and then the dark reaction mixture is transferred to aseparatory funnel and washed with H₂ O, aqueous NaHCO₃ and brine andthen dried over anhydrous magnesium sulfate. The solvents are removed invacuo and the residue is chromatographed on 300 g of silica gel (70-230mesh) affording an off-white solid which is further purified bytrituration with ether to give 14.45 g (45%) of the title product as awhite solid; tlc: benzene:ethyl acetate (1:1), silica gel GF, Rf=0.64.Recrystallization from ethyl acetate-hexane affords an analyticalsample, mp 82°-84°.

Method B

A solution of 1.6 g (9.55 mmol) dimethoxybenzylamine in 5 ml of CH₂ Cl₂is rapidly added at 0° to a solution of 1.06 g (10 mmol) freshlydistilled methyl glyoxylate in 15 ml CH₂ Cl₂. A slight exotherm occurredand water droplets appeared. Magnesium sulfate (5 g) is added and themixture stirred at 0° for 2 hours. Fresh magnesium sulfate (1.0 g) isadded, the magnesium sulfate removed by filtration under argon andwashed with a minimum of CH₂ Cl₂.

To a solution of 3.8 g (36 mmol) of azidoacetic acid (pumped in highvacuum 3 hr) in 125 ml of CH₂ Cl₂ is added 10.6 ml (76 mmol) oftriethylamine with cooling. Magnesium sulfate (3 gm) is added, themixture stirred 10 min at room temperature, filtered under argon andwashed with a 25 ml CH₂ Cl₂.

The azidoacetic acid solution is added at 0° to the imine, sufficientmethylene chloride is added to bring the total volume to 200 ml, thesolution cooled to 0° under argon and 5.3 ml (38 mmol) trifluoroaceticanhydride added slowly over 1/2 hr with vigorous stirring and cooling.The mixture is stirred for 1 hr at 0°, allowed to warm to roomtemperature, transferred to a separatory funnel, washed with water, 5%NaHCO₃, 2% phosphoric acid and 5% NaHCO₃, dried over magnesiumsulfate-charcoal; filtered and the filtrate is retreated twice withcharcoal and evaporated to dryness. The residue is dissolved in aminimum of ether and stored at -20° to allow crystallization.

The crystalline mass was isolated and washed with cold ether to give 1.9gm (64%) product, mp 79°-80.5°.

Method C

A solution of 1.6 g. of 2,4-dimethoxybenzylamine in 15 ml. of methylenechloride was shaken with an excess of magnesium sulfate then reactedwith 1.05 g. of methyl glyoxylate in 2 ml. of methylene chloride at 25°C. (room temperature) overnight. The mixture was filtered, stripped anddegassed with argon.

A solution of 1.5 g. of azidoacetic acid in 25 ml. of methylene chloridewas cooled to 0° C. then reacted with 1.3 ml. of oxalyl chloride with1.2 ml. of pyridine in 3 ml. of methylene chloride at 0° C. Argon waspassed through the mixture which was stirred for one hour.

The imine from above was taken into 20 ml. of methylene chloride with4.15 ml. of triethylamine. The solution of azidoacetyl chloride wasadded dropwise at 0° C. After one hour at 0° C. the mixture was washedwith water, sodium bicarbonate solution, salt solution, dried andstripped. After passing over a silica gel column with methylene chloridethe yield was 1.31 g. of the desired compound.

Substitution of ethyl glyoxylate, n-butyl, tert. butyl, benzyl ormethoxybenzyl glyoxylate for methyl glyoxalate gives the correspondingester congeners of the title compound.

EXAMPLE 2 Methylcis-1-(2,4-Dimethoxybenzyl)-3-amino-4-oxoazetidine-2-carboxylate

A mixture containing 10.0 g (0.0312 mole) of methylcis-1-(2,4-dimethoxybenzyl)-3-azido-4-oxoazetidine-2-carboxylate, 1.0 gof 10% palladium on carbon, and 200 ml of ethanol is hydrogenated for 2hrs at 40°-45° and 60 psi of hydrogen. The reaction mixture is allowedto cool to 25° and is filtered through filter-aid. After removing thesolvents in vacuo a clear, yellow gum of the title product is obtained.

EXAMPLE 3 Methylcis-3-t-Butoxycarbonylamino-1-(2,4-dimethoxybenzyl)-4-oxoazetidine-2-carboxylate

A solution of 5.5 g (18.8 mmole) of methylcis-3-amino-1-(2,4-dimethoxybenzyl)-4-oxoazetidine-2-carboxylate in 100ml of dry toluene is cooled to -78°; 2.5 ml (18.8 mmole) oftriethylamine is added followed by rapid addition of 35 ml (42 mmole) ofa 12% solution of phosgene in benzene. The mixture is stirred 15 min at-78°, 3 hr at -45° (acetonitrile-dry ice), then warmed to roomtemperature and concentrated to half volume in vacuum. To the resultingsolution is added 50 ml of t-butanol and the mixture is stirred at roomtemperature overnight. The solvents are removed in vacuum, the residueis diluted with ethyl acetate and filtered. The filtrate is transferredto a separatory funnel and washed with 5% NaHCO₃, 5% HCl and brine;dried over magnesium sulfate and evaporated to dryness.Recrystallization of the crude, crystalline product affords 3.8 g (52%)of the title compound. Recrystallization from ether gives an analyticalsample.

EXAMPLE 4 Methylcis-1-(2,4-Dimethoxybenzyl)-3-phthalimido-4-oxoazetidine-2-carboxylate

2,4-Dimethoxybenzylamine (5.01 g, 0.03 mol) and methyl glyoxolate (3.17g, 0.036 mol) are condensed as in Preparation 1 but at 0°-5° for 2hours. The resulting imine is dissolved in methylene chloride (800 ml)and cooled in an ice bath. Triethylamine (5.4 ml) is added followed bythe dropwise addition of a solution of N-phthalimido acetic acidchloride (7.54 g, 0.0338 mol) [J. Amer. Chem. Soc., 71, 1856 (1949)] inmethylene chloride (80 ml). After the reaction is stirred 2 hours, thesolution is concentrated and then is washed with water, dilute HCl, anddilute NaHCO₃. The dried organic phase is evaporated to give the titleproduct which is triturated with ether; 6.4 g (50%).

EXAMPLE 5 Methylcis-1-(2,4-Dimethoxybenzyl)-3-(4,5-diphenyl-2-oxo-4-oxazolin-3-yl)-4-oxoazetidine-2-carboxylate

The imine from Preparation 1 (1.43 g) is dissolved in dry methylenechloride (13 ml) and triethylamine (1 ml) and cooled in an ice bath. Theacid chloride from Preparation 2 (2.0 g, 6.4 mmol) in methylene chloride(10 ml) is added over a 10-minute period. After one hour, the mixture iswashed with water and 5% NaHCO₃, the dried solution is evaporated to ared oil which is chromatographed on 60 g of silica gel with 5% ethylacetate in chloroform as eluant to give the title product, 2.37 g.

EXAMPLE 6 Methylcis-1-(2,4-Dimethoxybenzyl)-3-phenoxyacetamido-4-oxo-2-azetidinecarboxylate

The crude amine prepared in Example 2 from 10 g of the azido precursoris taken up in 100 ml of anhydrous methylene dichloride and is cooled to0° in an ice bath. To this solution is added 4.32 ml (0.0312 mol) oftriethylamine followed by the slow addition of a solution of 5.32 g(0.0312 mol) of phenoxyacetyl chloride in 40 ml of methylene dichloride.The mixture is stirred at 0° for 1 hr. then poured into a separatoryfunnel and extracted successively with water, aqueous HCl, aqueousNaHCO₃, brine and is dried over anhydrous magnesium sulfate. Afterfiltration the solvent is removed in vacuo to give a yellow solid. Thismaterial is partially dissolved in ether, cooled to -25°, and filteredto afford 11.2 g (84%) of the title product as a white solid which isone spot on tlc: benzene-ethyl acetate (1:1), silica gel, Rf 0.38. Ananalytical sample, mp 115.5°-116.0°, is obtained by recrystallizationfrom ethyl acetate-hexane.

EXAMPLE 7

When p-methoxybenzyl alcohol, isoborneol, benzyl alcohol, or2,2,2-trichloroethanol is substituted for t-butanol in Example 3, methyl3-(p-methoxybenzyloxycarbonylamino)-1-(2,4-dimethoxybenzyl)-4-oxoazetidine-2-carboxylate,methyl3-(isobornyloxycarbonylamino)-1-(2,4-dimethoxybenzyl)-4-oxoazetidine-2-carboxylate,methyl3-(benzyloxycarbonylamino)-1-(2,4-dimethoxybenzyl)-4-oxoazetidine-2-carboxylate,or methyl3-(2,2,2-trichloroethoxycarbonylamino)-1-(2,4-dimethoxybenzyl)-4-oxoazetidine-2-carboxylateis obtained.

Methyl3-(isobornyloxycarbonylamino)-1-(2,4-dimethoxybenzyl)-4-oxoazetidine-2-carboxylatecan also be prepared by treating the 3-amino compound withisobornyloxycarbonyl chloride in the presence of base according tostandard procedures; Chem. Pharm. Bull., 20, 1017 (1972).

EXAMPLE 8 Methylcis-3-t-Butoxycarbonylamino-4-oxoazetidine-2-carboxylate

A solution of 10.5 g (26.7 mmole) of methyl3-t-butoxycarbonylamino-1-(2,4-dimethoxybenzyl)-4-oxoazetidine-2-carboxylatein 500 ml of acetonitrile is degassed with argon and warmed to 80°. Adegassed solution of 15 g (55.5 mmole) of potassium persulfate and 7.5 g(28 mmole) of sodium monohydrogen phosphate in 150 ml of water is addedin five portions over 1 hr. The reaction is stirred at 80°-85° underargon for 2-3 hrs until all starting material is consumed (tlc). Thereaction mixture is cooled, concentrated in vacuum, shaken with ethylacetate-water. The organic phase is washed with dilute HCl, NaHCO₃solution and brine; dried over magnesium sulfate and evaporated todryness. The residue is chromatographed over silica gel with 1:1benzene-ethyl acetate to afford pure product which crystallized fromethyl acetate-hexane to yield 2.0 g (31%) of the title compound. A lesspure fraction from the column, is crystallized from ethyl acetate-hexaneto give an additional 0.5 g of product, overall yield, 38%.

EXAMPLE 9

When the products of Examples 1, 4, 5, 6 and 7 are treated withpotassium persulfate and sodium monohydrogen phosphate according to theprocedure of Example 8 the following products are obtained:

methyl cis-3-azido-4-oxoacetidine-2-carboxylate; 72% yield mp 77°-78°

methyl cis-3-phthalimido-4-oxoazetidine-2-carboxylate; 40% yield

methylcis-3-(4,5-diphenyl-2-oxo-4-oxazolin-3-yl)-4-oxoazetidine-2-carboxylate,32% yield

methyl cis-3-phenoxyacetamido-4-oxoazetidine-2-carboxylate; 69% yield,mp 140°-41°

methyl cis-3-isobornylcarbonylamino-4-oxoazetidine-2-carboxylate

methylcis-3-(p-methoxybenzyloxycarbonylamino)-4-oxoazetidine-2-carboxylate

methyl cis-3-(benzyloxycarbonylamino)-4-oxoazetidine-2-carboxylate

methylcis-3-(2,2,2-trichloroethoxycarbonylamino)-4-oxoazetidine-2-carboxylate

EXAMPLE 10 Methyl cis-3-Amino-4-oxoazetidine-2-carboxylate

A solution of methyl cis-3-azido-4-oxoazetidine-2-carboxylate (8.5 g, 50mmol) and an equivalent of p-toluenesulfonic acid in 200 ml of ethanolis hydrogenated for 3 hours over 1 g of 10% Pd on carbon at 40 psi. Thesolution is filtered and the filtrate is evaporated to title product orthe tosylate salt which can be converted to the free base by standardmethods.

EXAMPLE 11

A solution of anhydrous K₂ CO₃ (249 mg, 1.8 mmol) in tetrahydrofuran (8ml) and water (12 ml) is degassed with argon and then methylcis-3-phenoxyacetamido-1-(2,4-dimethoxybenzyl)-4-oxoazetidine-2-carboxylate(150 mg, 0.35 mmol) is added. The reaction is stirred 1.5 hours at roomtemperature, the organic solvent is evaporated and the aqueous layer isacidified and extracted with methylene chloride. The dried extracts areevaporated to give a solid which is recrystallized from ethylacetate-hexane to give purecis-3-phenoxyacetamido-1-(2,4-dimethoxybenzyl)-4-oxoazetidine-2-carboxylicacid, mp 169°-170°(d).

Methyl cis-3-phenoxyacetamido-4-oxoazetidine-2-carboxylate is treatedwith K₂ CO₃ in methanol-water as above to givecis-3-phenoxyacetamido-4-oxoazetidine-2-carboxylic acid, mp 150°-51°from ethyl acetate.

EXAMPLE 12 cis-3-t-Butoxycarbonylamino-2-hydroxymethyl-4-oxoazetidine

A solution of 2.0 g (8.2 mmole) of methyl3-t-butoxycarbonylamino-4-oxoazetidine-2-carboxylate in 20 ml oftetrahydrofuran is cooled in ice and a solution of 0.75 g (20 mmole) ofsodium borohydride in 10 ml of water is added. The mixture is stirred 20min at 0° and then 1.5 hr at room temperature. Acetic acid is addeddrop-wise to decompose the excess borohydride and the mixture isconcentrated in vacuum. The residue is diluted with brine and extractedwith ethyl acetate. The organic phase is washed with brine and 5% NaHCO₃; dried over magnesium sulfate and evaporated to dryness to give 0.9 g(50%) of the title product as white crystals, mp 128°-131°.

EXAMPLE 13

When the 3-azido, 3-oxazolinyl, 3-phenoxyacetamido,3-isobornyloxycarbonylamino, 3-(p-methoxybenzyloxycarbonylamino, and3-benzyloxycarbonylamino compounds from Example 9 are reduced withsodium borohydride by the procedure of Example 12 the following productsare obtained:

cis-3-azido-2-hydroxymethyl-4-oxoazetidine; 56% yield

cis-2-hydroxymethyl-3-(4,5-diphenyl-2-oxo-4-oxazolin-3-yl)-4-oxoazetidine;ca. 100% yield

cis-2-hydroxymethyl-3-phenoxyacetamido-4-oxoazetidine; 68% yield, mp.153°-4° (from ethyl acetate)

cis-2-hydroxymethyl-3-isobornyloxycarbonyl-4-oxoazetidine

cis-2-hydroxymethyl-3-(p-methoxybenzyloxycarbonylamino)-4-oxoazetidine

cis-3-benzyloxycarbonylamino-2-hydroxymethyl-4-oxoazetidine

EXAMPLE 14 cis-3-t-Butoxycarbonylamino-4-oxo-2-azetidinylmethyl tosylate

To a solution of 0.9 g (4.3 mmole) of 98% p-toluenesulfonyl chloride in10 ml of dry pyridine at 0° is added 0.9 g (4.15 mmole) of3-t-butoxycarbonylamino-2-hydroxymethyl-4-oxoazetidine. The mixture isstirred for 2 hr at 0° and then stored at 5° overnight. After additionof 0.5 ml of 85% lactic acid, the mixture is stirred for 1 hr, pouredinto ethyl acetate and washed with dilute HCl, 5% NaHCO₃, and brine. Theextract is dried over magnesium sulfate and evaporated to dryness togive 1.1 g (70%) of crystalline title product. Recrystallization fromhexane-ethyl acetate gives an analytical sample, mp 160°-162° (d).

EXAMPLE 5

Treatment of the products obtained in Example 13 with p-toluenesulfonylchloride according to the procedure of Example 14 gives thecorresponding tosylates:

cis-3-azido-4-oxo-2-azetidinylmethyl tosylate; 80% yield mp 87°-89°

cis-3-(4,5-diphenyl-2-oxo-4-oxazolin-3-yl)-4-oxo-2-azetidinylmethyltosylate

cis-3-phenoxyacetamido-4-oxo-2-azetidinylmethyl tosylate; 71% yield, mp136° (d)

cis-3-isobornyloxycarbonylamino-4-oxo-2-azetidinylmethyl tosylate

cis-3-(p-methoxybenzyloxycarbonylamino)-4-oxo-2-azetidinylmethyltosylate

cis-3-benzyloxy carbonylamino-4-oxo-2-azetidinylmethyl tosylate

Whencis-2-hydroxymethyl-1-(2,4-dimethoxybenzyl)-3-(4,5-diphenyl-2-oxo-4-oxazolin-3-yl)-4-oxoazetidineis reacted according to Example 13 except that mesyl chloride issubstituted for p-toluenesulfonyl chloride,cis-3-(4,5-diphenyl-2-oxo-4-oxazolin-3-yl)-4-oxo-2-azetidinylmethylmesylate is obtained; 73% yield, mp 185°-8° from ethyl acetate-hexane.

EXAMPLE 16 cis-3-Amino-4-oxo-2-azetidinylmethyl tosylate

A solution of cis-3-azido-4-oxo-2-azetidinylmethyl tosylate (5.0 g) in50% aqueous acetic acid (50 ml) is cooled and then treated with zincdust (2.0 g). The reaction is stirred for 30 minutes, filtered, and thesolid washed with H₂ O (50 ml). The filtrate is saturated with H₂ S over1/2 hour, the zinc sulfide is removed by filtration and the filtrateevaporated to near dryness. The residue is dissolved in ethylacetate-water and adjusted to pH 10. Phases are separated and theaqueous layer is extracted with ethyl acetate. The dried organic phasesare evaporated to give the amino compound; 3.0 g (66%).

EXAMPLE 17

A mixture of the 3-amino tosylate compound from Example 16 (0.14 g),N-t-butoxycarbonylphenylglycine (0.16 g) and dicyclohexylcarbodiimide(0.12 g) in methylene chloride (5 ml) is stirred one hour at 0° C. Thesolid is removed by filtration and the filtrate is evaporated todryness. The residue is chromatographed on silica gel with 80:20 ethylacetate-benzene as eluant to givecis-3-(α-t-butoxycarbonylaminophenylacetamido)-4-oxo-2-azetidinylmethyltosylate; 0.19 g (70%).

2-Thienylacetic acid, the 3-amino derivative from Example 16, anddicyclohexylcarbodiimide (3.7 mmol of each) is reacted in methylenechloride as above. The mixture is diluted with ethyl acetate (150 ml)and filtered; the filtrate is washed with 5% NaHCO₃, dilute HCl, andbrine, dried, evaporated and crystallized from acetone-ether to givecis-3-(2-thienylacetamido)-4-oxo-2-azetidinylmethyl tosylate; 0.9 g(69%) mp 121°-124°.

The 3-amino derivative is acylated with O-formylmandelic acid chloridein the presence of triethylamine to givecis-3-formylmandelamido-4-oxo-2-azetidinyl methyl tosylate, 98% mp111°-113° (dec).

EXAMPLE 18 cis-3-Phenoxyacetamido-4-oxo-2-azetidinemethyl iodide

A mixture containing 13.68 g (33.9 mmol) ofcis-3-phenoxyacetamido-4-oxo-2-acetidinemethyl tosylate, 39.8 g (0.265mol) of sodium iodide and 550 ml of acetone is heated at reflux for aperiod of 6 hr and then is allowed to cool to ambient temperature. Theacetone is removed in vacuo and the residue is suspended in ethylacetate and extracted with water, sodium thiosulfate and brine. Thedried ethyl acetate solution was evaporated in vacuo to give a yellowsemi-crystalline residue. Recrystallization from ethyl acetate resultedin 10.3 g (84%) of crystalline product; mp 150° (dec).

EXAMPLE 19

When the appropriate tosylate or mesylate which are disclosed in Example14, 15 and 17 is treated with sodium iodide by the procedure disclosedin Example 18 the following products are obtained:

cis-3-t-butoxycarbonylamino-4-oxo-2-azetidinylmethyl iodide

cis-3-azido-4-oxo-2-azetidinylmethyl iodide

cis-3-(4,5-diphenyl-2-oxo-4-oxazolin-3-yl)-4-oxo-2-azetidinylmethyliodide

cis-3-(α-t-butoxycarbonylaminophenylacetamido)-4-oxo-2-azetidinylmethyliodide, 78% yield

cis-3-thienylacetamido-4-oxo-2-azetidinylmethyl iodide, 98% yield

cis-3-formylmandelamido-4-oxo-2-azetidinylmethyl iodide

cis-3-isobornyloxycarbonylamino-4-oxo-2-azetidinylmethyl iodide

cis-3-(p-methoxybenzyloxycarbonylamino)-4-oxo-2-azetidinylmethyl iodide

cis-3-benzyloxycarbonylamino-4-oxo-2-azetidinylmethyl iodide

EXAMPLE 203-t-Butoxycarbonylamino-4-oxo-2-(p-methoxybenzylthiomethyl)-azetidine

To a solution of 1.1 g (2.97 mmole) of3-N-t-butoxycarbonylamino-4-oxo-2-azetidinylmethyl tosylate in 15 ml ofdry dimethylformamide under argon was added 4.0 g (26 mmole) of sodiumiodide. The mixture was heated to 65° for 4 hours, then stirred at roomtemperature overnight. The resulting suspension was diluted with 50 mlof ethyl acetate, filtered, concentrated in vacuum, flushed with argonand 3.0 ml of p-methoxybenzyl mercaptan and 2.0 ml of triethylamine wereadded. The mixture was stirred at room temperature for 18 hours and thenpoured into ice water-ethyl acetate. The organic phase was separated andwashed with water, 5% NaHCO₃ and brine; dried over magnesium sulfate andevaporated to dryness. The residue was chromatographed over silica gelwith 1:1 benzene-ethyl acetate to afford after evaporation andcrystallization from ethyl acetate-hexane, 335 mg (32%) of pure product,mp 120°-123°.

EXAMPLE 21

When an appropriate iodide derivative is reacted with p-methoxybenzylmercaptan (2 equivalents) in the presence of triethylamine (2equivalents) according to the procedure set forth in Example 20 thefollowing compounds are obtained

cis-3-phenoxyacetamido-4-oxo-2-(p-methoxybenzylthiomethyl)azetidine; mp139°-41°

cis-3-formylmandelamido-4-oxo-2-(p-methoxybenzylthiomethyl)azetidine

cis-3-(α-t-butoxycarbonylaminophenylacetamido)-4-oxo-2-(p-methoxybenzylthiomethyl)azetidine

cis-3-isobornylcarbonylamino-4-oxo-2-(p-methoxybenzylthiomethyl)azetidine

cis-3-(p-methoxybenzyloxycarbonylamino)-4-oxo-2-(p-methoxybenzylthiomethyl)azetidine

cis-3-benzyloxycarbonylamino-4-oxo-2-(p-methoxybenzylthiomethyl)azetidine

EXAMPLE 22cis-3-(2-Thienylacetamido)-4-oxo-2-(triphenylmethylthiomethyl)azetidine

To a solution of 0.8 g (2.3 mmole) ofcis-3-(2-thienylacetamido)-4-oxo-2-azetidinemethyl iodide and 0.9 g (9mmole) of triethylamine in 10 ml of dry dimethylformamide is added 1.27g (4.6 mmole) of triphenylmethanethiol. The mixture is stirred underargon overnight, diluted with 100 ml of ethyl acetate and washed withdilute HCl and water. After drying with magnesium sulfate, the extractis evaporated to dryness and the residue triturated with ether. Thecrystalline product is filtered and dried to give the title compound.

EXAMPLE 23

When the methyl iodide derivatives of Examples 18 and 19 are reactedwith triphenylmethanethiol according to the procedure of Example 22 thefollowing compounds are obtained.

cis-3-phenoxyacetamido-4-oxo-2-(triphenylmethylthiomethyl)azetidine

cis-3-t-butoxycarbonylamino-4-oxo-2-(triphenylmethylthiomethyl)azetidine

cis-3-(4,5-diphenyl-2-oxo-4-oxazolin-3-yl)-4-oxo-2-(triphenylmethylthiomethyl)azetidine

cis-3-(α-t-butoxycarbonylaminophenylacetamido)-4-oxo-2-(triphenylmethylthiomethyl)azetidine

cis-3-formylmandelamido-4-oxo-2-(triphenylmethylthiomethyl)azetidine

cis-3-isobornyloxycarbonylamino-4-oxo-2-(triphenylmethylthiomethyl)azetidine

cis-3-(p-methoxybenzyloxycarbonylamino)-4-oxo-2-(triphenylmethylthiomethyl)azetidine

cis-3-benzyloxycarbonylamino-4-oxo-2-(triphenylmethylthiomethyl)azetidine

EXAMPLE 24 3-t-Butoxycarbonylamino-4-oxo-2-mercaptomethylazetidine

To a solution of 335 mg (0.95 mmole) of3t-butoxycarbonylamino-4-oxo-2-(p-methoxybenzylthiomethyl)azetidine in 5ml of methanol and 20 ml of methylene chloride is added 1.7 g (5.3mmole) of mercuric acetate. The mixture is stirred 24 hours under argon,diluted with excess ether and the precipitated mercury adduct filteredand washed well with ether. The mercury complex is suspended in water,layered with ethyl acetate and hydrogen sulfide gas is passed throughthe mixture for 1 hour. The mercuric sulfide is removed by filtration,the ethyl acetate layer is separated and washed with brine, dried overmagnesium sulfate and evaporated to dryness. Trituration of the residuewith 1:1 ethyl acetate-hexane gives 122 mg (55%) of the crystallinetitle product.

EXAMPLE 25 cis-3-(2-Thienylacetamido)-4-oxo-2-mercaptomethylazetidine

To a solution of 0.l g (0.2 mmole) ofcis-3-(2-thienylacetamido)-4-oxo-2-(triphenylmethylthiomethyl)-azetidinein 3 ml of methanol is added a solution containing 34 mg (0.2 mmole) ofsilver nitrate and 16 mg (0.2 mmole) of pyridine. A precipitate of thesilver mercaptide is formed immediately. Hydrogen sulfide gas is passedthrough the mixture for 5 minutes, the silver sulfide removed byfiltration and the filtrate diluted with ethyl acetate and washed withdilute HCl and brine. The extract is dried and evaporated to dryness;trituration with ether gives the title compound as white crystals.

EXAMPLE 26

When the p-methoxybenzylthiomethyl derivatives prepared in Example 21are deblocked according to the procedure of Example 24 the followingcompounds are obtained.

cis-3-phenoxyacetamido-4-oxo-2-mercaptomethylazetidine

cis-3-formylmandelamido-4-oxo-2-mercaptomethylazetidine

cis-3-(α-t-butoxycarbonylaminophenylacetamido)-4-oxo-2-mercaptomethylazetidine

cis-3-isobornyloxycarbonylamino-4-oxo-2-mercaptomethylazetidine

cis-3-(p-methoxybenzyloxycarbonylamino)-4-oxo-2-mercaptomethylazetidine

cis-3-benzyloxycarbonylamino-4-oxo-2-mercaptomethylazetidin

Similarly when the triphenylmethylthiomethyl derivatives prepared inExample 23 are deblocked by the procedure set forth in Example 25 thecorresponding mercaptomethyl compounds are obtained.

EXAMPLE 27

A solution of methylcis-3-(4,5-diphenyl-2-oxo-4-oxazolin-3-yl)-4-oxoazetidine-2-carboxylate(2.0 g, 3.9 mmol) in 50 ml ethanol is added to 10% Pd on carbon (0.5 g)which is premoistened with 2 ml 2 N HCl. The mixture is hydrogenated for12 hours at 50 psi and 40° C. After filtration, the solvent is removedand the oil is dissolved in methylene chloride which is then washed withNaHCO₃ and brine and dried. The solution is evaporated to give methylcis-3-amino-1-(2,4-dimethoxybenzyl)-4-oxoazetidine-2-carboxylate.

EXAMPLE 28 Trichloroethyl7β-t-Butoxycarbonylamino-6αH-2-hydroxy-8-oxo-4-thia-1-azabicyclo[4.2.0]octane-2-carboxylate

To a suspension of 122 mg (0.52 mmole) ofcis-3-t-butoxycarbonylamino-4-oxo-2-mercaptomethylazetidine in 20 ml ofmethylene chloride is added 156 mg (0.52 mmole) of trichloroethylbromopyruvate followed at 0° by 50 μl of triethylamine. Methanol (5 ml)is added to effect solution and the mixture is stirred at roomtemperature for 1 hour. The solvents is removed in vacuum, the residueis dissolved in ethyl acetate which is washed with dilute HCl, 5% NaHCO₃and brine; dried over magnesium sulfate and evaporated to dryness. Theresidue is chromatographed over silica gel with 1:2 ethylacetate-benzene to afford 80 mg (35%) of the title product as a mixtureof diastereomers.

EXAMPLE 29 Trichloroethyl7β-amino-6αH-8-oxo-4-thia-1-azabicyclo-[4.2.0]oct-2-ene-2-carboxylate

Method A

To a solution of 70 mg (0.156 mmole) of the product from Example 28 in 3ml of dry ethyl acetate is added 0.2 ml pyridine and 150 mg ofmethanesulfonyl anhydride. The mixture is stirred overnight at roomtemperature and then diluted with water. The aqueous solution isextracted with ethyl acetate and the extracts are washed with dilute HCland 5% NaHCO₃ and then dried. Evaporation gives a residue which ischromatographed on silica gel with 80:20 benzene-ethyl acetate aseluant. The product (50 mg) is a mixture of the desired trichloroethylcis-7-t-butoxycarbonylamino-8-oxo-4-thia-1-azabicyclo-[4.2.0]oct-2-ene-2-carboxylateand the 7-methylsulfonylamino derivative but separation before thefollowing deblocking reaction is not necessary.

The above mixture is dissolved in 2 ml of methylene chloride, cooled to0° and treated with 0.5 ml trifluoroacetic acid for 0.5 hr at 0°. Thesolution is washed with 5% NaHCO₃ and then extracted with dilute HCl.The aqueous phase is neutralized and extracted with ethyl acetate. Theextracts are dried and then acidified with ethereal HCl. Thehydrochloride salt of the title product is collected.

Method B

To a solution of the product from Example 28 (150 mg) in ethyl acetate(4 ml) is added pyridine (150 μl). The solution is cooled to -10° C.,stirred 1 hour with thienyl chloride (50 μl), diluted with water,acidified and extracted with ethyl acetate. The extracts are washed with5% NaHCO₃, and brine, dried and evaporated. The product is purified anddeblocked as in Method A.

EXAMPLE 30

When cis-3-t-butoxycarbonylamino-4-oxo-2-mercaptomethylazetidine iscondensed with benzhydryl bromopyruvate by the procedure of Example 28,benzhydryl7β-t-butoxy-carbonylamino-6αH-2-hydroxy-8-oxo-4-thia-1-azabicyclo-[4.2.0]octane-2-carboxylateis obtained. Dehydration by either of the methods set forth in Example29 gives benzhydryl7β-t-butoxycarbonylamino-6αH-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylate.

Similarly as described above, use of t-butyl bromopyruvate gives the twocompounds described above as their t-butyl ester.

EXAMPLE 317β-Amino-6αH-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid

Method A

To a solution of 43 mg (0.1 mmole) of trichloroethylcis-7-t-butoxycarbonylamino-8-oxo-4-thia-1-azabicyclo-[4.2.0]oct-2-ene-2-carboxylatein 6 ml of dimethylformamide and 6 l ml of acetic acid is added over a1.5 hr period 250 mg (3.8 mmole) zinc dust. The mixture is stirredvigorously for 3 hrs and then diluted with 50 ml of water. The mixtureis acidified with dilute HCl, filtered and extracted with ethyl acetate.The organic phase is extracted with 5% NaHCO₃ which is acidified andreextracted into ethyl acetate. The final extracts are washed withbrine, dried, and evaporated to givecis-7-t-butoxycarbonylamino-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacid.

The above product is dissolved in methylene chloride and treated withtrifluoroacetic acid as outlined in Example 29. The reaction isevaporated in vacuo and the residue is triturated with ether to give thetrifluoroacetate salt of the title product. The salt is dissolved inwater and treated with basic ion-exchange resin ("Amberlite IR-45")until constant pH is obtained. After filtration, the aqueous solution islyophilized to give the title product.

Method B

The ethyl acetate solution of trichloroethylcis-7β-amino-6αH-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylatefrom Example 29 is treated with acetic acid and zinc dust as describedabove in Method A. After stirring 3 hrs, the reaction solution isacidified to pH 2 with dilute HCl, filtered, and evaporated to dryness.The residue is treated with basic ion-exchange as in Method A to givethe title product.

Method C

A solution of benzhydryl7β-t-butoxycarbonylamino-6αH-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylate(1 mmol) in methylene chloride is treated with trifluoroacetic acid at0° as in Example 29, to cleave the two blocking groups and give thetitle compound.

EXAMPLE 32 Benzhydryl7β-phenoxyacetamido-6αH-2-hydroxy-3-methyl-8-oxo-4-thia-1-azabicyclo[4.2.0]octane-2-carboxylate

To a stirred solution of 0.234 g (0.88 mmol) ofcis-3-phenoxyacetylamino-4-oxo-2-mercaptomethylazetidine and 0.304 g(0.88 mmol) benzhydryl 3-bromo-2-ketobutyrate in 26 ml of dry methylenechloride is added 122 μl (0.88 mmol) of triethylamine at roomtemperature under argon. The solution is stirred for 1 hr, then themethylene chloride is removed in vacuo and the residue dissolved inethyl acetate. The ethyl acetate solution is washed with 3 N HClsolution, 5% NaHCO₃ solution and saturated NaCl solution. After drying,the solution is evaporated in vacuo to give 0.531 g of crude product.Chromatography of 0.466 g of crude product on silica gel eluting withethyl acetate-hexane affords 320 mg of benzhydryl7β-phenoxyacetamido-6αH-2-hydroxy-3-methyl-8-oxo-4-thia-1-azabicyclo[4.2.0]octane-2-carboxylateas a foam. (78%)

EXAMPLE 33 Benzhydryl 7β-phenoxyacetamido-6αH-3-methyl-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylate

To a stirred solution of 0.200 g (0.39 mmol) of benzhydryl7β-phenoxyacetamido-6αH-2-hydroxy-3-methyl-8-oxo-4-thia-1-azabicyclo[4.2.0]octane-2-carboxylateand 282 μl trifluoroacetic anhydride in 4 ml of dry ethyl acetate isadded dropwise 161 μl (2.0 mmol) pyridine at 0° under argon. Thesolution is allowed to come to room temperature and stirred for 20hours. The reaction mixture is diluted with ethyl acetate and washedtwice with 5% NaHCO₃, 3 N HCl, and brine. The ethyl acetate layer isdried over MgSO₄ and concentrated in vacuo to afford 300 mg crudeproduct. Chromatography on silica gel eluting with 50:50 ethylacetate/benzene gives 21.8 mg (11%) of white, crystalline benzhydryl7β-phenoxyacetamido-6αH-3-methyl-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylateand 42.1 mg (21%) of recovered starting material mp 155°-156°.

EXAMPLE 347β-Phenoxyacetamido-6αH-3-methyl-8-oxo-4-thia-1-azabicyclo-[4.2.0]oct-2-ene-2-carboxylicacid

A solution of 0.062 g (1.2×10⁻⁴ mol) of benzhydryl7β-phenoxyacetamido-6αH-3-methyl-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylate,125 μl anisole, and 0.7 ml of trifluoroacetic acid in 2 ml of methylenechloride is stirred at 0° under argon for 1.3 hours. The trifluoroaceticacid and methylene chloride are removed in vacuo and the residue istreated with ethyl acetate and dilute HCl. The ethyl acetate isextracted with 5% NaHCO₃, and the aqueous combined extracts acidified toa pH of 1.5 and reextracted into ethyl acetate. The combined organicextracts are dried over MgSO₄, filtered and concentrated. After pumpingunder high vacuum, 25.2 mg of a yellow solid is isolated. Precipitationfrom methylene chloride-hexane solution afforded 18.7 mg (44%) ofanalytically pure title compound, mp 205°-15° (dec).

EXAMPLE 35 t-Butyl 7β-phenoxyacetamido-6αH-2-hydroxy-3-methyl-8-oxo-4-thia-1-azabicyclo[4.2.0]octane-2-carboxylate

To a stirred solution of 0.083 g (0.31 mmol) ofcis-3-phenoxyacetamido-4-oxo-2-mercaptomethylazetidine and 0.084 g (0.31mmol) t-butyl 3-bromo-2-ketobutyrate in 10 ml of dry methylene chlorideis added 44 μl (0.31 mmol) of triethylamine at room temperature underargon. The solution is stirred for 1.25 hours, the methylene chlorideremoved in vacuo, and the residue dissolved in ethyl acetate. The ethylacetate is washed with 3 N HCl, 5% NaHCO₃ and brine. After drying, thesolution is evaporated in vacuo to give 0.120 g of crude product.Chromatography on silica gel eluting with 50:50 ethyl acetate-hexanegives 93.8 mg (70%) of a colorless oil. After standing at roomtemperature, the oil solidified to give crystalline title compound, mp138°-150°.

EXAMPLE 36 t-Butyl7β-phenoxyacetamido-6αH-3-methyl-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylate

To a stirred solution of 0.302 g (0.72 mmol) of the 2-hydroxy compoundfrom Example 35 and 200 μl (1.43 mmol) of trifluoroacetic anhydride in 6ml dry ethyl acetate is added dropwise 290 μl (3.58 mmol) of pyridine at0° under argon. The solution is allowed to come to room temperature andstir overnight (20 hrs). The reaction mixture is diluted with ethylacetate and washed with 5% NaHCO₃, 3 N HCl and brine. The ethyl acetatesolution is dried over MgSO₄ and concentrated. Chromatography on silicagel eluting with ethyl acetate-hexane mixture affords 49.5 mg (17%) ofthe title compound as a yellow solid, mp 147°-149°.

EXAMPLE 37

Substitution ofcis-3-t-butoxycarbonylamino-4-oxo-2-mercaptomethylazetidine for thephenoxyacetamido derivative in the procedures of Examples 33 and 35gives the benzhydryl and t-butyl esters of7β-t-butoxycarbonylamino-6αH-2-hydroxy-3-methyl-8-oxo-4-thia-1-azabicyclo-[4.2.0]octane-2-carboxylicacid.

The above esters are each treated with trifluoroacetic anhydride by theprocedure in Examples 33 and 36 or with the other dehydrating agents setforth in Example 29 to give benzhydryl and t-butyl7β-t-butoxycarbonylamino-6αH-3-methyl-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylate.

Treatment of either of the above esters with trifluoroacetic acid by theprocedure in Example 34 gives7β-amino-6αH-3-methyl-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacid.

EXAMPLE 38 t-Butyl7β-Phenoxyacetamido-6αH-3-bromomethyl-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylate

A suspension of 30.0 mg (0.075 mmol) of t-butylcis-7β-phenoxyacetamido-6αH-3-methyl-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylateand 28 mg (0.15 mmol) of N-bromosuccinimide in 5 ml of carbontetrachloride is degassed, a trace of azobisisobutyronitrile is addedand the mixture refluxed for 2 hrs. After cooling, the mixture isfiltered, evaporated to dryness, redissolved in ethyl acetate, washedwith 5% sodium bisulfite, dried over magnesium sulfate and evaporated todryness. The residue was chromatographed on silica gel with 5% ethylacetate in chloroform to give on trituration with methylenechloride-hexane, 10.8 mg of the title compound as a pale yellowamorphous solid.

EXAMPLE 397β-Phenoxyacetamido-6αH-3-acetoxymethyl-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacid

A mixture of 48 mg (0.1 mmole) of the bromomethyl derivative fromExample 38 and 200 mg of silver acetate in 10 ml of acetone is stirredat room temperature for 1 day. The mixture is filtered, the filtrate isevaporated to dryness and chromatographed over silica gel with 5% ethylacetate in chloroform to afford the t-butyl ester of the title compound.

The above material is dissolved in ice cold trifluoroacetic acidcontaining 10% anisole. The solution is stirred at 0° for 1/2 hr, thesolvent is removed in vacuum, the residue is dissolved in ethyl acetateand extracted with 5% sodium bicarbonate solution. The aqueous extractis carefully acidified and extracted with ethyl acetate, the extract isdried over magnesium sulfate and evaporation to dryness. Triturationwith hexane affords the title compound.

EXAMPLE 40

When the t-butyl7β-t-butoxycarbonylamino-6αH-3-methyl-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylateis treated with N-bromosuccinimide by the procedure of Example 38,t-butyl7β-t-butoxycarbonylamino-6αH-3-bromomethyl-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylateis obtained.

Treatment of the above bromomethyl derivative with sodium acetate orsilver acetate according to the procedure of Example 39 gives t-butyl7β-t-butoxycarbonylamino-6αH-3-acetoxymethyl-8-oxo-4-thia-1-azabicyclo-[4.2.0]oct-2-ene-2-carboxylate

When the above compound is treated with trifluoroacetic acid by theprocedure of Example 39,7β-amino-6αH-3-acetoxymethyl-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacid is obtained.

EXAMPLE 41 Trichloroethyl7β-Phenoxyacetamido-6αH-2-hydroxy-8-oxo-4-thia-1-azabicyclo[4.2.0]octane-2-carboxylate

To a solution of 273 mg (1.02 mmol) ofcis-3-phenoxyacetamido-4-oxo-2-mercaptomethylazetidine and 305 mg (1.02mmol) of trichloroethyl bromopyruvate in 30 ml of methylene chloride isadded slowly at 0°, 0.110 ml triethylamine. After stirring for two hoursat room temperature, the mixture is evaporated to dryness, the residueis dissolved in ethyl acetate, washed with 5% HCl, 5% NaHCO₃, andsaturated NaCl, evaporated to dryness and chromatographed over silicagel with 1:1 ethyl acetate-hexane as eluant to give the title product,256 mg (52%).

EXAMPLE 427β-Phenoxyacetamido-6αH-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-4-carboxylicacid

To a cooled solution (0° C.) of 0.477 g (1 mmol) of trichloroethyl7β-phenoxyacetamido-6αH-2-hydroxy-8-oxo-4-thia-1-azabicyclo[4.2.0]octane-2-carboxylatein 10 ml ethyl acetate is added 65 μl of trifluoroacetic anhydride andthen 362 μl of pyridine. The reaction is stirred overnight at roomtemperature and then diluted with ethyl acetate. The solution is washedwith NaHCO₃ solution, 3 N NCl and saturated saline solution. The driedsolution is evaporated to give the ester of the title product which isrecrystallized from benzene; 157 mg (34%).

In 24 ml solution of dimethylformamide-glacial acetic acid (1:1) isdissolved 70 mg of the above ester. To this solution is added over a 1.5hour period 500 mg of zinc dust which has been treated with 5% HCl for 3minutes, washed with water, ethanol, and ether and then dried. Thereaction mixture is stirred 3 hours at room temperature, diluted withwater, acidified with 3 N HCl and extracted with ethyl acetate. Theextracts are washed with a large volume of 5% NaHCO₃. The aqueoussolution is acidified to pH 2 with HCl and extracted with ethyl acetate.The dried extracts are concentrated in vacuo and then high vacuum isused to remove residual acetic acid. The residue is triturated withether-hexane, dissolved in methylene chloride and precipitated withhexane to give the title product, mp 194°-5°(dec).

EXAMPLE 437β-(α-Aminophenylacetamido)-6αH-8-oxo-4-thia-1-azabicyclo-[4.2.0]oct-2-ene-2-carboxylicacid

Benzhydryl bromopyruvate (500 mg) was dissolved in benzene (8 ml) andtetrahydrofuran (1 ml), cooled to 10° C. and treated with a solution ofdiphenyldiazomethane (286 mg) in benzene (10 ml). The solution isstirred until colorless and then evaporated to dryness. The residue isdissolved in methylene chloride (5 ml) and cooled to 0° C. and thencis-3-(α-t-butoxycarbonylaminophenylacetamido)-4-oxo-2-mercaptomethylazetidine(465 mg) is added. The reaction is stirred for one hour and evaporatedto dryness to give a residue which dissolved in ethyl acetate-water. Theethyl acetate phase is washed with 1% HCl, NaHCO₃ solution and NaClsolution. The dried organic phase is evaporated to give benzhydryl7-(α-t-butoxycarbonylaminophenylacetamido)-2-hydroxy-8-oxo-4-thia-1-azabicyclo[4.2.0]octane-2-carboxylate.

To a solution of the above product (200 mg) in ethyl acetate (4 ml) isadded pyridine (150 μl). The solution is cooled to -10° C., stirred onehour with thionyl chloride (50 μl), diluted with water, acidified andextracted with ethyl acetate. The extracts are washed with 5% NaHCO₃ andNaCl solution, dried and evaporated. The residue is chromatographed oversilica gel with 5:1 benzene-ethyl acetate as eluant to give the blockedderivative of the title product (50 mg).

The blocking groups are removed by stirring a solution of the aboveproduct (118 mg) in methylene chloride (10 ml), anisole (0.2 ml) andtrifluoroacetic acid (2.0 ml) for 45 minutes at 0° C. under argon. Thereaction is allowed to warm to room temperature and then is evaporatedto dryness under high vacuum. The trifluoroacetate salt of the titlecompound is triturated with ether and reprecipitated frommethanol-ether.

EXAMPLE 447β-(α-Amino-p-hydroxyphenylacetamido)-6αH-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacid

To a solution of 265 mg (1 mmol) ofN-t-butoxycarbonyl-p-hydroxyphenylglycine in dry tetrahydrofuran (10 ml)is added triethylamine (0.14 ml). After cooling to -10°, isobutylchloroformate (1 mmol) in 2 ml of tetrahydrofuran is added dropwise andthe reaction is stirred 20 minutes. A mixture of 270 mg (1 mmol) ofcis-3-amino-4-oxo-2-azetidinemethyl tosylate and 0.14 ml oftriethylamine in 50% aqueous tetrahydrofuran (5 ml) is cooled to -10°and added to the reaction solution. The resulting solution is stirredone hour at low temperature and then allowed to warm to roomtemperature. The organic solvent is removed and the aqueous residue isdiluted with water and extracted with ethyl acetate. The aqueoussolution is layered with ethyl acetate, cooled and acidified. Phases areseparated and the aqueous layer is extracted with ethyl acetate. Thedried organic layers are evaporated to give thecis-3-(α-t-butoxycarbonylamino-p-hydroxyphenylacetamido)-4-oxo-2-azetidinylmethyltosylate.

The above tosylate is reacted with NaI followed by p-methoxybenzylmercaptan according to the procedure of Example 20 to give thep-methoxybenzylthio derivative which is cleaved by the procedure ofExample 24 to givecis-3-(α-t-butoxycarbonylamino-p-hydroxyphenylacetamido)-4-oxo-2-mercaptomethylazetidine.

The above product is reacted with benzhydryl bromopyruvate according tothe procedure of Example 43 and the subsequent reaction sequencedisclosed therein is continued to give the title product.

EXAMPLE 457β-(2-Thienylacetamido)-6αH-8-oxo-4-thia-1-azabicyclo-[4.2.0]oct-2-ene-2-carboxylicacid

The dry ethyl acetate solution from Example 29 of trichloroethyl7β-amino-6αH-8-oxo-4-thia-1-azabicyclo-[4.2.0]oct-2-ene-2-carboxylatewhich is obtained from 0.012 g of the t-butoxycarbonyl derivative istreated with 0.2 ml 2-thienylacetyl chloride and 0.2 ml oftriethylamine. The reaction is stirred 2 hours at room temperature andthen diluted with NaHCO₃ solution. The organic layer is separated,washed with 3 N HCl, dried, and evaporated to give the7-thienylacetamido derivative.

The above ester is treated with zinc dust and acetic acid according tothe procedure in Example 42 to give the title product.

EXAMPLE 467β-Phenoxyacetamido-6αH-8-oxo-4-thia-1-azabicyclo[4.2.0]-oct-2-ene-2-carboxylicacid

The dry ethyl acetate solution of trichloroethyl7β-amino-6αH-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylatefrom Example 29 is cooled to 0° and treated with one equivalent each ofphenoxyacetyl chloride and triethylamine. After stirring one hour, themixture is washed with dilute HCl and brine. The organic phase is driedand evaporated to give trichloroethyl ester of the title product.

The trichloroethyl ester was treated with zinc dust and acetic acid bythe procedure given in Example 42 to give the title product.

EXAMPLE 477β-Methylsulfonylacetamido-6αH-8-oxo-4-thia-1-azabicyclo-[4.2.0]oct-2-ene-2-carboxylicacid

A solution of 200 mg (1 mmol) of trichloroethyl7β-amino-6αH-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylate and0.14 ml triethylamine in 10 ml of dimethylformamide is stirred with 236mg (1 mmol) of the N-hydroxysuccinimide ester of methylsulfonylaceticacid for two hours at room temperature. The reaction is poured into icewater and the resultant solution is extracted with ethyl acetate. Theaqueous phase is acidified to pH 2 and extracted with ethyl acetate. Thedried extracts are evaporated to give the ester which is deblocked as inExample 42 to give the title product.

EXAMPLE 48

When trichloroethyl7β-amino-6αH-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acidis acylated with one of the following carboxylic acids:

α-formyloxyphenylacetic acid

trifluoromethylmercaptoacetic acid

methylmercaptoacetic acid

2,2,2-trifluoroethylsulfinylacetic acid

cyanoacetic acid

cyanomethylmercaptoacetic acid

cyanomethylsulfinylacetic acid

cyanomethylsulfonylacetic acid

α-carboxy-2-thienylacetic acid

α-carboxy-3-thienylacetic acid

α-sulphophenylacetic acid

3-thienylacetic acid

1-tetrazolylacetic acid

using the acid or an activated derivative thereof, all of which areknown in the art, and which have any sensitive or interfering groupsuitably protected, according to known acylation procedures such asthose set forth in Examples 43, 44, 45 or 47 followed by removal of allprotecting groups by standard methods, gives the corresponding7β-acylamino-6αH-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacid.

EXAMPLE 49

When α-(N-t-butoxycarbonylamino)-4-hydroxy-3-fluorophenylacetic acid orα-(N-t-butoxycarbonylamino)-4-(t-butoxycarbonylmethylamino)phenylaceticacid is substituted for N-t-butoxycarbonyl-p-hydroxyphenylglycine inExample 44, the following compounds are obtained:

7β-(α-amino-4-hydroxy-3-fluorophenylacetamido)-6αH-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacid

7β-(α-amino-4-carboxymethylaminophenylacetamido)-6αH-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacid.

EXAMPLE 507β-(α-Carboxyphenylacetamido)-6αH-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacid

Equimolar quantities of the N-hydroxysuccinimidyl ester ofα-t-butoxycarbonylphenylacetic acid, cis-3-amino-4-oxo-2-azetidinemethyltosylate and triethylamine are stirred together in dimethylformamide fortwo hours at room temperature. The reaction is poured into ice water andthe aqueous solution is washed with ethyl acetate, acidified to pH 2 andextracted with ethyl acetate. The dried extracts are evaporated to givethe cis-3-(α-t-butoxycarbonylphenylacetamido)-4-oxo-2-azetidinylmethyltosylate.

When the above tosylate is substituted for the tosylate in Example 44and the reaction sequence disclosed therein is continued, the titleproduct is obtained.

EXAMPLE 51

When7β-amino-6αH-3-methyl-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacid is acylated with 2-thienylacetic acid, phenoxyacetic acid,methylsulfonylacetic acid, α-formyloxyphenylacetic acid,trifluoromethylmercaptoacetic acid, 2,2,2-trifluoroethylsulfinylaceticacid, cyanoacetic acid, cyanomethylmercaptoacetic acid,cyanomethylsulfinylacetic acid, cyanomethylsulfonylacetic acid,α-carboxy-2-thienylacetic acid, α-carboxy-3-thienylacetic acid,α-sulphophenylacetic acid, 3-thienylacetic acid, 1-tetrazolylaceticacid, α-aminophenylacetic acid, α-amino-p-hydroxyphenylacetic acid,α-amino-4-hydroxy-3-fluorophenylacetic acid,α-amino-p-carboxymethylaminophenylacetic acid, or α-carboxyphenylaceticacid, using the acid itself or an activated derivative thereof all ofwhich are known in the art and which have any sensitive or interferringgroups suitably protected, according to known acylation procedures suchas those set forth in Examples 43, 44, 45 or 47 followed by removal ofall protecting groups by standard methods, the corresponding7β-acylamino-6αH-3-methyl-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacid is obtained.

EXAMPLE 52

When7β-amino-6αH-3-acetoxymethyl-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacid is acylated with 2-thienylacetic acid, phenoxyacetic acid,methylsulfonylacetic acid, α-formyloxyphenylacetic acid,trifluoromethylmercaptoacetic acid, 2,2,2-trifluoroethylsulfinylaceticacid, cyanoacetic acid, cyanomethylmercaptoacetic acid,cyanomethylsulfinylacetic acid, cyanomethylsulfonylacetic acid,α-carboxy-2-thienylacetic acid, α-carboxy-3-thienylacetic acid,α-sulphophenylacetic acid, 3-thienylacetic acid, 1-tetrazolylaceticacid, α-aminophenylacetic acid, α-amino-p-hydroxyphenylacetic acid,α-amino-4-hydroxy-3-fluorophenylacetic acid,α-amino-p-carboxymethylaminophenylacetic acid, or α-carboxyphenylaceticacid, using the acid itself or an activated derivative thereof all ofwhich are known in the art and which have any sensitive or interferinggroups suitably protected, according to known acylation procedures suchas those set forth in Examples 43, 44, 45 or 47 followed by removal ofall protecting groups by standard methods, the corresponding7β-acylamino-6αH-3-acetoxymethyl-8-oxo-4-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylicacid is obtained.

EXAMPLE 53 Methylcis-3-amino-1-(2,4-dimethoxyphenyl-4-oxoazetidine-2-carboxylate

The lactam product from Example 4 (8.0 g) was cooled in adry-ice-acetone bath under nitrogen then 1.1 g of methylhydrazine added.After stirring for 20 minutes the mixture was re-cooled to -78° C. and4.5 ml of the hydrazine added. The volatiles were removed at the pump togive 8.3 g of half opened hydrazide intermediate. This compound (3.5 g)in 50 ml of chloroform was heated on the steam bath for 30 minutes thenallowed to stand several days. The liquid was evaporated to give ayellow oil of mostly cis-3-amino compound which may be optionallypurified over a silica gel column using chloroform-isopropanol.

The yellow oil in 25 ml of methylene chloride cooled to 0° C. wasreacted with 1.3 g of phenoxyacetyl chloride and 1 ml of triethylamineto give the 3-phenoxyacetamido derivative, m.p. 114.5°-115.5° C.

EXAMPLE 54 A. n-Butyl cis-1-benzhydryl-3-azido-4-oxo-2-azetidinecarboxylate (2)

To a mixture containing 4.16 g (22.7 mmole) of benzhydrylamine andanhydrous magnesium sulfate in 50 ml of dichloromethane at 25° C. wasadded a solution of 2.96 g (22.7 mmole) of n-butyl glyoxylate in 50 mlof dichloromethane. The reaction mixture was stirred at room temperatureovernight and then was filtered and the solvents were removed in vacuoto afford the imine.

To a solution of 2.29 g (22.7 mmole) of azidoacetic acid in 100 ml ofanhydrous dichloromethane at 0° C. under an argon atmosphere was addeddropwise 3.1 ml (22.7 mmole) of trifluoroacetic anhydride. The solutionwas stirred at 0° C. for 10 min then 3.15 ml (22.7 mmole) oftriethylamine was added dropwise and stirring was continued at 0° C. foran additional 20 min. To this light-yellow solution at 0° C. undr argonwas added a solution of the imine generated above (theo. 22.7 mmole) and3.15 ml (22.7 mmole) of triethylamine in 50 ml of dichloromethane. Thereaction mixture was stirred at 0° C. for 1 hour and then was stirred atambient temperature overnight.

The resulting dark brown reaction mixture was extracted once with water,three times with dilute aqueous hydrochloric acid and twice with aqueoussodium bicarbonate. The dichloromethane extracts were combined and driedover anhydrous magnesium sulfate and the solvents were removed in vacuoto afford 6.3 g of dark brown oil. This material was chromatographed ona column of 130 g of Silica Gel (70-230 Mesh) and the desired β-lactamwas removed with 50% ethylacetate-benzene to afford 1.68 g (19.5%) as ayellow solid. Recrystallization of this material from hexanethylacetateresulted in a white crystalline solid with m.p. 101.5°-102.5° C.

B. Butyl cis-3-azido-4-oxo-2-azetidinecarboxylate (3)

A mixture of 200 mg (0.529 mmole) of butylcis-1-benzhydryl-3-azido-4-oxo-2-azetidine carboxylate, 473 mg (1.75mmole) of potassium persulfate, 307 mg (0.858 mmole) of disodiumphosphate dodecahydrate, 9.2 ml of water and 8.4 ml of acetonitrile wasthoroughly degassed with argon and then heated to 80°-85° C. under argonfor three hours. The reaction mixture was cooled and the acetonitrileremoved on the rotary evaporator. The aqueous residue was saturated withsolid sodium chloride and extracted three times with ethyl acetate. Thecombined organic extractions were washed with brine, dried overanhydrous sodium sulfate, filtered, and concentrated in vacuo to give197 mg of crude material. This material was chromatographed on ten gramsof 70-230 mesh silica gel and 31 mg (28%) of the desired product, alight yellow foam was eluted with 20% EtOAc in benzene. tlc: silica gelGF; 20% ethylacetate benzene, R.f.=0.15.

Various methoxy substituted benzhydrylamines can be substituted in thesereactions such as 4-methoxybenzhydrylamine,4,4'-dimethoxybenzhydrylamine, 2,3-dimethoxybenzhydrylamine,2,2',4,4'-tetramethoxybenzhydrylamine. Also equimolar quantities ofother glyoxalates may be used such as benzyl glyoxalate, isoamylglyoxalate, hexyl glyoxalate, trichloroethyl glyoxalate orp-methoxybenzyl glyoxalate.

EXAMPLE 55

The "protected" and "acyl" glycines, their acid chlorides and mixedanhydrides are prepared and used employing methods known to the art, forexample in Greenstein and Winitz, Chemistry of the Amino Acids, Volume2, pages 924-945, 965-982 or E. H. Flynn, Cephalosporins andPenicillins, Chapter 16, Academic Press (1972), or P. G. Sammes, Chem.Rev. 76, 113 (1976).

Substituting molar equivalents of the following acylating agents in themethods detailed in Examples 1, 4 or 5 gives the azetidinones of Formula3a in which alk is methyl.

    ______________________________________                                        Acylating agent   3a when A is:                                               ______________________________________                                        N-(t.-butoxycarbonyl)-glycyl                                                                    t.-butoxycarbonylamino                                      chloride                                                                      N-(trichloroethoxycarbonyl)-                                                                    trichloroethoxycarbonyl-                                    glycyl chloride   amino                                                       N-(carbobenzoxy)-glycyl                                                                         benzyloxycarbonylamino                                      isobutylcarbonate                                                             phenoxyacetamidoacetyl                                                                          phenoxyacetamido                                            chloride                                                                      O-benzylmandeloylglycyl                                                                         O-benzylmandeloylamino                                      chloride                                                                      D-α-t.-butoxycarboxamido-                                                                 D-α-t.-butoxycarboxamido-                             phenylacetamidoacetyl-trifluoro-                                                                pheylacetamido                                              acetic anhydride                                                              O-formylmandeloylglycyl                                                                         O-formylmandeloylamino                                      chloride                                                                      2,6-dimethoxybenzoylglycyl                                                                      2,6-dimethoxybenzoylamino                                   chloride                                                                      p-nitrobenzoylglycyl bromide                                                                    p-nitrobenzoylamino                                         N-tritylglycyl chloride                                                                         tritylamino                                                 N-(iso-bornyloxycarbonyl)-                                                                      isobornyloxycarbonylamino                                   glycyl chloride                                                               N-(p-methoxybenzylcarbonyl-                                                                     p-methoxybenzylcarbonyl-                                    glycyl chloride   amino                                                       cyanoacetamidoacetyl chloride                                                                   cyanoacetamido                                              methyl-1-tetrazolylacetamido-                                                                   methyl-1-tetrazolylaceta-                                   acetyl chloride   mido                                                        N-succinimidoacetamidoacetyl                                                                    succinimidoacetamido                                        acetyl cloride                                                                N-maleimidoacetamidoacetyl                                                                      maleimidoacetamido                                          chloride                                                                      ______________________________________                                    

EXAMPLE 56

Substituting molar equivalents of each end product described in Example55 into the persulfate procedure of Example 6 using reactiontemperatures from -75° to 0° C. gives the corresponding debenzylatedazetidinone.

EXAMPLE 57

The product of Example 10, methylcis-3-amino-4-oxoacetidine-2-carboxylate, is acylated using either themixed anhydride procedures known in the cephalosporin-penicillin artsuch as those referred to in the Flynn reference of Example 54 (page677) or the reaction with a substituted acetyl chloride (page 666). Thissequence of reactions is preferred to that of Example 54, that is formonovalent amine groups which are formed with great difficulty or forthio-containing acylamino compounds which are not susceptible tohydroxyl radical supplying oxidation agents. α-Thienylacetyl chloridegives methyl cis-3-α-thienylacetamido-4-oxoacetidine-2-carboxylate;4-pyridylthioacetyl chloride in dimethylformamide with triethylaminegives methylcis-3-α-(4-pyridylthio)acetamido-4-oxoazetidine-2-carboxylate;trifluoroethylsulfinylacetyl chloride gives methylcis-3-2,2,2-trifluoroethylsulfinylacetamido-4-oxoazetidine-2-carboxylate;O-formyl-D-mandeloyl chloride gives methylcis-3-D-mandeloylamino-4-oxoazetidine-2-carboxylate, O-formyl ester;t.-boc of D-p-hydroxyglycine anhydride with trichloroethyl chloroformategives after reaction and removal of the t.-boc protecting group withtrifluoroacetic acid methylcis-3-D-p-hydroxyglycylamino-4-oxoazetidine-2-carboxylate.

Each of these intermediates are reacted further in Scheme I, compound 5to 8 and 9.

EXAMPLE 58

Substituting p-methoxybenzylamine in the cyclization reaction describedabove gave4-carbomethoxy-3-phthalimido-1-(p-methoxybenzyl)azetidin-2-one, m.p.141°-142°.

A solution of 2.45 g (6.22 mmol) of the azetidinone in 250 ml ofacetonitrile and 75 ml of water was degassed with argon. At 80°, adegassed solution of 23.5 g (87.2 mmol) of potassium persulfate and 7.77g (55 mmol) of disodium phosphate was added in 6 portions over 1 hour.The mixture was cooled, the acetonitrile removed in vacuum, the aqueousresidue saturated with sodium chloride and extracted with warm (40°)hexane (3×100 ml) then with ethyl acetate (5×125 ml). The ethyl acetateextract was washed with sodium bicarbonate, brine, dried and evaporatedto dryness. Titration with ether gave4-carbomethoxy-3-phthalimido-azetidin-2-one, m.p. 124°-6°.

The deblocking of the ring nitrogen atom using persulfate givesexcellent yields and is not dependent of the 2 or 3 substituents whichare inert to persulfate. For example, the reaction has been run witharomatic alkyl or acyl groups at position 2 to give good yields. Mostcommonly the 1-benzyl blocked acetidinone is reacted with 14 molarequivalents of potassium persulfate, 9 molar equivalents of disodiumphosphate in aqueous acetonitrile at elevated temperatures such as atreflux for 1/2 to 11/2 hours.

EXAMPLE 59

As an example of the utility of the end products prepared according tothis invention, following is the in vitro spectrum of the compound ofExample 45,7β-(2-thienylacetamido)-6αH-8-thia-1-azabicyclo[4.2.0]-oct-2-ene-2-carboxylicacid along with the spectra of three commercially useful anti-bacterialagents. Based on such comparative data to evaluate efficacy and potencythe end products prepared as described herein may be used as topical orsystemic anti-bacterial agents in the same manner as the prior artcephalosporins or penicillins.

                                      TABLE 1                                     __________________________________________________________________________     MINIMUM INHIBITORY CONCENTRATION μg/ml)                                   __________________________________________________________________________    1            2       3       4      5      6     7      8                                          Staph. aureus               Kleb.  Kleb.                 Staph. aureus                                                                              Staph. aureus                                                                         Villafuz (M.R.)                                                                       Staph. faecalis                                                                      E. coli                                                                              E. coli                                                                             pneumoniae                                                                           pneumoniae            HH 127       SK & F 23390                                                                          SK & F 70399                                                                          HH 34358                                                                             SK & F 12140                                                                         HH 33779                                                                            SK & F                                                                               SK & F                __________________________________________________________________________                                                            1200                  Pen G.                                                                             6.3     0.1     200     0.8    6.3    12.5  1.6    12.5                  Cephalo-                                                                           0.2     0.1     25      12.5   1.6    3.1   0.8    0.8                   thin                                                                          Cefazolin                                                                          0.2     0.2     100     3.1    0.8    0.8   0.8    0.4                                        >       >                                                Ex.45                                                                              25      12.5    200     200    12.5   25    6.3    6.3                   __________________________________________________________________________                      9      10    11    12     13   14     15                                      Salmonella   Pseudo.                                                                             Serratia                                                                             Proteus                                                                            Enterobacter                                                                         Enterobacter                            paratyphi                                                                            P. mirabilis                                                                        aeruginosa                                                                          marcescens                                                                           morgani                                                                            aerogenes                                                                            cloacae                                 ATCC 12176                                                                           PM -444                                                                             HH 63 ATCC 13830                                                                           179  ATCC 13048                                                                           HH                    __________________________________________________________________________                                                            31254                                                             >                                              Pen G.                                                                             0.8    1.6   200   12.5   200  12.5   6.3                                Cephalo-          >     >      >                                              thin 0.4    3.1   200   200    200  12.5   12.5                                                 >                                                           Cefazolin                                                                          0.4    3.1   200   100    100  0.8    0.8                                                  >            >                                              Ex. 45                                                                             3.1    50    200   200    200  2.5    25                    __________________________________________________________________________

What is claimed is:
 1. A compound of the structure ##STR12## in which: Ais azido, amino or blocked amino;B is --CH₂ X¹ ; X¹ is OM, halo,methoxybenzylthio, triphenylmethylthio or mercapto; M is hydrogen, loweralkylsulfonyl or phenylsulfonyl said phenyl being unsubstituted orsubstituted with a methyl or halo; and Z is hydrogen,2,4-dimethoxybenzyl, benzhydryl or methoxy substituted benzhydryl. 2.The compound of claim 1 in which A is blocked amino, B is CH₂ OH, and Zis hydrogen.
 3. The compound of claim 2 in which A ist.-butoxycarbonylamino.
 4. The compound of claim 1 in which A ist.-butoxycarbonylamino, B is --CH₂ I and Z is hydrogen.
 5. The compoundof claim 1 in which A is t.-butoxycarbonylamino, B is --CH₂ SH and Z ishydrogen.
 6. The compound of claim 1 beingcis-3-azido-2-tosyloxymethyl-4-oxoazetidine.